When my kids were 9, 9 & 10 I took them to Europe for a total of 5 weeks (hubby joined us for two of those weeks).
We were not in a motorhome but stayed in youth hostels, B&B's and travelled via trains, busses, and occasionally taxi for short distances. I prepared them well what to expect. The night before I had second guesses about doing this by myself with them; I had done it alone many times. I need not have worried.
There were many new experiences which puts them on their best behavior (which they were pretty good anyway). We explored castles (in Ireland, Scotland) and I realized pretty quickly (think behavior) that they needed time to explore areas on their own and not drive around on buses for too long. Schedules are good but when they want to explore something more...that was the way to go.
Think moderation and kid stuff and they will be happy an so will you!
Schedules are made to be broken.
We did another trip when they were 14, 14, and 15. Norway was fabulous and they were troopers travelling by bus, boat, train,plane, and foot.