First of all, good for you! I also drove alone with my 2 kids from NH to Ft. Pierce, FL, to see my parents, years ago when they were 8 and 11. I asssume you are the Mom, as I am.
First, figure how far you want to get the first night. If you don't have a good atlas, get one, and calculate your mileage. I remember deciding to make it halfway, which for me was in NC. I checked out all the Days Inns on I95 and found the best price, made a reservation and that was the first day's mission. There are web sites for all the major motel chains, and also
http://www.usastar.com/i95/homepage.htm
which is excellent for finding anything on 95 from Maine to Florida.
Depending on your taste, the I 95 site link above will give you virtually every restaurant on every I95 exit, so you can pick and choose.
I 95 is so easy, you should have no problem. I grew up going to FL every other Christmas with my parents, from PA to Coral Gables (near Miami), so maybe I am more comfortable with the ride than some, but it really is a breeze.
If you have any other specific questions, shoot, but this should get you started. Good luck and have fun!