As mentioned..lugging a "bigger than you will need", heavier, larger 5th wheel Toy Hauler when you merely need comfortable living quarters for the kids and 2 adults will probably be overkill.
You'll find a family/kid friendly 5er will be easier to tow, more comfortable for the kids, most likely an overall better layout for the little guys.
Just some Examples-
1) The Jayco Seismic Toy Hauler 5er 3210 Model is 37 ft long, weighs 12,500 lbs dry, 16,500 gvwr, carries 148 gallons of fresh water and comes with a fuel tank and generator you don't need.
2) On the other hand, the Jayco Eagle 34.5 BHTS is 38' long, 10,233 dry, 12,995 loaded gvwr. Kids get their very own private bunk room with either 3 bunks or 2 bunks and a sofa with a TV hutch and closets. They also have their own rear entry door, their own 1/2 bathroom with rear toilet/sink too! You may not see them for days! ;)
By the way....a Standard outside kitchen, sink, refrig too!
Look at Forest River products (Rockwood, Wildcat, Sierra, etc), Heartland, Crossroads, Prime Time etc for some great RV's from terrific companies that meet your needs. Good luck!