C.V.
Wait until you can no longer contain him in the crib. He's happy there and there's no reason at this point to force a transition.
Once he's uncontainable in the crib, buy a regular, twin sized bed and mattress. Leave the bed in the box and put it in the garage or storage room, and just put the mattress right on the floor...no worrying about little guy falling out of bed. Once he's used to it and sleeping reliably on the mattress without rolling off, you can put the bed together and put the mattress on it.
Easy breezy.
♥
C. Lee