I personally found the wedge no good anymore when my kids could kick or move out of it and really a waste of time and energy trying to keep them in it. As far as crawling and moving around, yep it definitely can be a disturbance to winding down for sleep for a few weeks or so. Can you pop him down for a nap 15mins sooner, so he gets lots of crawling time in there? What about just leaving him to crawl around or are you saying that he gets frustrated and starts to cry, or does the crying only start when you intervene? I think you'll find, that going to sleep for a nap will be forever altered, he will probably like to do a final bit of crawling at naptime as his own winddown - well I've found that with my kids anyway. If he is getting upset, I'd just continue to reassure, I probably wouldn't bother to reposition him if he's not stuck, but just say reassuring words to the effect that it's time for sleep etc and let him sleep whereever he chooses in the crib. Also, when my kids were strong enough and were able to rol onto tummy'sl I let them sleep in whatever position they chose - but that's your call.
HTH