Depends mostly on (all of) YOU. Can everybody commit to that kind of schedule and gracefully stick to it. Else you'll travel/arrive/tour/return/REMEMBER miserable. Not what family vacation's about.
If you have two drivers it'd be a huge help, even if one's a 400-miler and the other only a 100-miler. And if you can have a copilot/navigator/you-still-awaker.
We tend to run the RV much slower than our car or van, so we don't get the same distance per hour/per day.
We also find the RV isn't anywhere near as easy to drive, so each mile takes more concentration and is more tiring.
If you drive well and the coach handles well, and you decide to run speed limit plus, fuel mileage will be atrocious. 5MPG wouldn't surprise me. Can you deal with that vs the maybe 8 you'd get at a lower speed?