We take our two oldest grandchildren (both 13 yrs old now)traveling with us during their summer vacations. They've done this for four years now. Yes, much more work for both of us...it's hard to believe how much a 13 yr old eats, let alone grey tanks, black tanks, fresh water tanks, ice, etc. etc. That said, it's fun to have them experience travel to (them) exotic places and different States.
There are alternatives. Many campgrounds have cabins for rent that aren't as expensive as hotels/motels. If they can't afford a large family tent, perhaps you could find one on Craigslist, Goodwill, EBay etc and present it to them as a Christmas "gift". We used to tow a tent trailer behind the coach for the kids to sleep in. Cooking was done in the rig, but the kids slept in the trailer.
It's been my experience that visitors don't understand the RVing lifestyle, especially if you're on a fixed income. One of my rules is if I supply the RV, you supply the food and beverages. My rig only sleeps TWO, but I've slept as many as six before and wow! short stays only! Surprising how small the RV becomes as the days pass.....Dennis