You have the prayers of me and my family as well.

I hope you are able to find a good boat for you and your family. A little extra bit here, from a guy who has a 4 year old, and several nephews that like to take boat rides. My daughter (4) is big on swimming, but doesn't necessarilly love to go tubing. If she does go, it's with an adult, and not very fast. So, this may be a good bit of info for you, in that you probably won't need any engine larger than a 75hp or even 60hp motor, as long as the boat isn't longer than 22 feet. If you're looking in the 18 foot range, those motors are plenty of power for your family right now. In 2-5 years, maybe they will want to go faster, but you can gain a TON of experience by then, just by being on the water.
Good luck to you.