Very sorry I missed this thread! Wow! good for you Med (and congrats btw).
As you probably know, our kiddos started off about 5 days aboard. We have cruised/LA on and off since then. Chase is now 12 yo.
First, car seat was always our standby. But we also found this bouncing chair to be great:
Not sure if they still make it. But what we liked was it would be quick and easy to get him out with. It also was more comfortable than the car seat. FOr us, where we sailed, our temps got very hot so the cumbersome car seats were always a concern.
As far as the engine noise, we are in some ways still living with that! However, ours isn't the engine noise, it was a fan. Chase always has a fan on now to sleep. That is a thought for others too to consider for investment. They are cheap and as LA/Cruisers, very neceesary. SO try giving him/her the white noise of a fan instead. Our favorite are the Caframo 747. They are very easy on power and the kids can stick their fingers in them and it won't cause any damage to either.
Down below, we always let teh kids take off their vest and do what they want. I believe that should be legal in WA too (I know it is in FL). Getting a nice tv or something that occupies them is almost a must. Does not have to be a tv. It can be something like a special car or toy. But there will be times mom and dad need to be top side to take care of things if possible. That being said, yes, you will both need to be able to single the boat. Now you see why I am such a big proponent of both parents singlehanding!! Reality for us though is that I do that vast majority of the sailing and she does the vast majority of the kids at sea. If she gets seasick though, you might consider a different arrangement.
I am a long time fan of Mustang life jackets. They come in infant sizes (I gave mine to Giulietta/Alex who used to post here). You may be able to pick one up from another family. we give ours away when the kids are too big for them. I just gave away my last one or I would send it to you. However, those don't work great in a car seat. Too big (at least in our expderience) and too hot. Wife will probably end up holding the little one when the LJ is on. The USCG never once bothered us about that. I think it is one of those things that they kinda understand. THat being said, if you start putting him or her in the jackeet now, they will become very accostomed to it and all its uncomfortableness. The jacket is still worth it though until they are proficient swimmers.
You need to look into a way to secure the hatch from the inside (for night and sometimes during the day). Before long, little junior will learn to crawl and going up the companionway steps will become very appealing. Ours did, but never got out. That is a nightmare scenario for a parent - esp at night.
Also, biggest chance of falling overboard is not at sea but at anchor/marina. The lifejackets come off and mom and dad are generally at ease. Our kids have gone in twice, both at the marina, and they have a LOT of sea miles under their belt. Food for thought when in the marina. And the water up there is COLD. I know. We spent time up there.
Boats are pretty much already childproof. Exceptions seem to be the nav station and battery switches. If your panel is keyed, maybe remove the key and keep it out of sight.
We made Chase a very comfortable Vberth arrangement where it was like a pen and he was surrounded by pillows. This came in handy more times than I can remember (esp when coming into a new anchorage or marina where 2 people are really awesome). This was also his bed and he was very comfortable there. In fact, he's asleep there right now with his brother. THe pic below is with my mom holding Chase and you can just see the Vberth arrangement to port. We made a "crib side" that blocked off the vberth so that when he wanted he could stand at it and peek over and still see us. THis is really good again when 4 hands are needed. Seeing mom/dad really helps:
The life is Awesome with kids Med. Not sure I will enjoy it as much without. I am happy to help anyway I can and answer any questions you have. I do not pretend to be an expert of anything. I can only show you what worked (and didn't) for us. Congratulations. Good to have you posting on this sided of the forum now! Tell your wife the same and she is always welcome to chat with my wife about mom-sailing stuff.
PS THis is a taste of what you have to look forward to: