20 Feet and under can be a challenge with a couple of younger kids - that size range is usually only a sleeping and cooking unit - no bathroom or shower, so limits types of campgrounds most likely to provide the missing elements. Certainly do-able, but something in the mid 20 foot range will probably cost about the same, but provide substantially more needed features.
Good luck, welcome to the group, and happy RVing!
John Day....|'88 Winnebago Super Chief 27ft. Class A
Eastern .....|'88 KIT model 240 24 ft. 5er
Oregon ......|'02 Dodge/Cummins 2500 Quad Cab