So our dog Dexter is a 40lbs English Staffie. He loves sailing, it totally tires him out with all the waves and motion (at least in big seas), when the waves and swell are down below 6 ft we need to keep an eye on him, because he will wander the deck when we are not paying attention. So get them a life jacket and or a harness.
Train him/her that it is ok to sh!@ near or on the house (like a deck). You should have no issue transitioning to the boat.
Dogs are the best defence system on a boat (even small ones) the locals in the Caribbean are deathly afraid of them and they are early alert systems.
You can buy dog food everywhere, just not the kind they like. If your dog is picky about food, that might be an issue.
Getting in and out of the dingy can be an issue if your freeboard is too high.
try and get them to not pee into the open hatches
have a wash down hose
Marinas and other cruisers can get real fussy about dogs. It is a huge PITA.
We took Dex for two passages so far, a 4 day passage and a 7 day one. He was fine. If you can find a water dish that doesn't spill.. bonus!