I agree wth HSM - let him at it. I worried about DS2 going from cot to bed. He climbed out of his cot one night so the next morning we put a bed in his room - he was only 18 months old. We put him to bed (in a bed) that night and he slept through without any issues - didn't seem to phase him in the slightest. We have also moved house since then, so it's a bit backward to what you've done, but he also adapted to the new room really well too. He loves to jump on his bed and climbs onto the bedhead - I've given up worrying about him falling and breaking something (a bone or something).

Love the bed by the way - I'm sure he'll love it too.