I don't think that taking your turtle outdoors can do anything but good for him. I take my tortoises outside to graze and just let them wander around freely while i watch. They graze on clover and dandelion and attempt to catch bugs...they love it! I keep mine in bins like yours and in a few months were planning on moving them to kiddy pools as well. Just make sure they cant climb out. Also check out this site it has care sheets and lots of other great articles.

Good luck!
World Chelonian Trust