How to handle a grumpy old man deva?

Sorry, not necessarily cancer related (except I think the project in question would be quite therapeutic to me as a cancer patient), but it seems likesome very creative people post here, so I thought I'd throw out my problem. I live in an assisted living facility with people quite a bit older than me, but we get along well. I have written a short play in something of the format of OTR, for two of the other residents and myself to do. Charlie was initially really excited to do it, but he's being a bit of a butt lately. We are planning to perform for the other residents in about a week, and I can't get him to settle on a time to rehearse. I suppose it's nerves reading in front of what probably won't amount to 15 other people. Most of the other male residents are not quite "all there" enough to deal with it, so I can't really replace him. I knew he would be perfect as an Edgar Kennedy "slow burn" type of character, and when he did the practice read it fit him like a glove. I don't want to be a pest because I'm afraid he'll just out refuse. This little skit means alot to me, and to the other woman who is in it.
Any suggestions?