There is a lot of good advice in this discussion, but at the heart of it, I would strongly back the suggestion to buy a small inexpensive boat for your first boat and sail the living daylights out of her. This will be the least expensive and fastest way to learn to sail and decide if the sailing life is for you.
There are a thousand little decisions in building a boat, decisions that you don't always know that you are making. These decisions can be small and insignificant, or they can make a boat a pain in the butt to sail. While an experienced sailor may make some minor mistakes, unless you understand how a boat operates, its easy to make far more serious errors, even building a simple dinghy.
Once you start to learn more about sailing, you can try to crew for folks or do trips to look at and perhaps sail on a range of boats. Once you have spent some time sailing and looking at the range of choices out there, you might still elect to build your own boat, but you would also understand why the James Cook would make a really lousy choice for what you are proposing to do with her.
I apologize that what follows is pretty long, and that I wrote this for another discussion but hopefully it may be helpful to you as you pursue your dreams.....
"The dream of voyaging under sail can be a powerful one. There was a period when several times a month I would receive an email from someone who is considering doing just what you are proposing. I have watched literally dozens of folks go through this. Some are successful in getting 'out there', some discover that they really enjoy sailing and find that they really have no need to 'go out there’; some have discovered that the sailing life is just not for them, and others have not even gotten past the dreaming stage.
From what I have seen, the most successful have been the ones who have been somewhat systematic about going. There is a lot to learn before one can safely venture offshore. No one would assume that they could buy a jet airliner take a few lessons and be able to fly around the world. I think most rational people would expect to start with a small plane and work their way up. But for some reason people assume that they can just go out and buy a big boat, take a couple lessons, read a few books, and then go safely cruising.
While there are people who literally taken a few lessons, read a few books and went out cruising, those that were successful following that route are far more rare than those who have done some kind of apprenticeship. Learning to sail and learning to cruise involves a lot of knowledge and no matter how much you know, there will always be more to learn, but I suggest that you at least take the time to learn the basics, and that just about can’t happen if you buy ‘a big sailboat’ and move your family aboard.
I find myself saying this a lot lately, but here I go again. We all come to sailing with our own specific needs, our own specific goals and our own specific capabilities. The neat thing about sailing is that we all don’t have to agree that there is only one right way to go sailing. There is no more truth in expecting that there is one universally right answer about many aspects of sailing than there is in trying to prove that vanilla ice cream is universally better than strawberry ice cream. One area of sailing for which there is no one universally right answer involves the amount of knowledge one requires to go sailing.
For some, all they need or want to know about sailing is just enough knowledge to safely leave the slip sail where they want and get back safely. There is nothing inherently wrong with that approach. Lack of knowledge will impact the level of risk, cost, comfort, and performance, but if you want to get out there with minimal knowledge it can be done. But for others, like myself, there is much more to sailing than simply developing a rudimentary knowledge of sailing basics. If you fall into that camp, it is next to impossible to learn to sail really well on a boat as large as the one in question.
While I am in no way suggesting that this makes sense for everyone, for those who really want to learn to sail well, I strongly suggest that they start out buying either a dinghy (14-18 feet) if they are athletically inclined, or else buying a used 23 to 27 foot, responsive, light-weight, tiller steered, fin keel/spade rudder (ideally fractionally rigged) sloop. Boats like these provide the kind of feedback that is so necessary to teach a newcomer how to really sail well. Boats like these have small enough loads on lines and the helm that you, your spouse and your children if you have them, can all participate and learn together. Being able to learn and participate, the children will be more engaged and less likely to be bored and feel kidnapped.
By sailing well, I mean understanding the nuances of boat handling and sail trim in a way that cannot be learned on a larger boat. Used small boats generally hold their values quite well so that after a year or even few years or so of learning, you should be able to get most of your money out of the small boat and move on to a bigger boat actually knowing something about which specific desirable characteristics of a boat appeal to you as an experienced sailor rather than the preferences of some stranger on some Internet discussion group.
From the advice that you have already gotten you can tell that there will not be a consensus of opinion on how to go distance cruising.
In any event, if I were in your shoes, I would sit down and put together a list of all of the things that I would want to know before I set off voyaging such as:
• Boat handling
• Sail trim
• Rules of the road
• Weather
• Routing
• Boat husbandry, repair and maintenance
• Diesel/ gas engine maintenance and repair
• First aid
• Heavy weather tactics
• Legal restrictions on leaving and entering foreign countries
• Navigation, (Piloting, Celestial, dead reckoning and electronic)
• Provisioning
• Radio operators license exam requirements
• Safe and dangerous fish to eat
• Survival skills
• Etc………..
Once I had what I thought was a complete list, I would set up a schedule to try to develop those areas of skill that I was currently lacking. As much as possible, if there are others involved, I would try to involve all those involved in as many of those aspects as each is capable of understanding. This process could take as little as a year, but more often takes two to three years. The process itself can be very rewarding and can build the kind of skills and knowledge set that would be required to be cast away on that oh so small island that a boat underway represents. But in the course of learning about sailing and boat types, you may also learn enough about yourself that your goals may change along the way. In the end, it is only you who sets your goals, and its only you that gets to change them. There is no sin in changing what you want to do. The only sin is not dreaming in the first place. "
Respectfully,
Jeff