This site might help you with all the different configurations of RVs, floorplans and prices. Note that there are different sections - for gas motorhomes, diesel motorhomes, Class C & Bs and trailers. Each one has pros and cons and no one can tell you which is best. It's up to you.
http://www.pplmotorhomes.com/classa/class-a-motorhomes.phpHow long do you plan to take a trip - all winter or just a few weeks. This could make a difference.
Your children will need space. Bunks are very popular nowadays. Having them sleep on the converted dinette or sofa can get tiresome for long periods of time. You'd all need to go to sleep at the same time and fixing and taking down the beds 2x/day isn't fun. You'll also need to store the bedding each day.
Some have recommended Park Model trailers left stationery in a RV park. This is fine for family-type places for summer use but if you want to go south you'll be looking at parks that cater to retirees and may not let you stay with children.
Re: Your concern for a trailer - between the two, a 5th wheel handles a lot better than a travel trailer and is easier to park.
Good luck!