Psychlist on 1/1/2015 8:40:35 AM:
35 miles / day sounds like a good manageable distance for a 10 year old - should be a great trip. My only suggestion is to get out for long training rides several times before then so you can be sure that the daily distance will be a piece of cake. Also at least one camping trip ahead of time to "shake out" your equipment, making sure you have all the camping equipment you need and that it all works as expected. You don't want to be at the first night's camp site, with darkness rapidly falling, puzzling over how to set up the tent (been there done that :-)
Good luck and Have fun!