2 month old bunnies being outdoors?

I use to have a bunnie who lived to be 12. he stayed outside during good days in his hutch. now i have two 2 month old bunnies. The bunnies are now to young to stay in it, but when they get older i will put them in the hutch. The ground is dirt and pebbles and they are unable to get to any plants from being in it. I am not sure if i should clean the cage with something or if i should put gr in there? Or should i just leave it because my last bunnie was fine with it (he loved being out there) :) Please answer and if you have any websites please let me know. I can't find any