Ohhhh, that's a tough one. I'm not really sure how to handle that. Maybe you should bring up your family shower in front of them, saying something about how where your MIL is going to have it etc and then talk about you have to go to the store to register (unless you've already done that, then you could just bring up the registry in a different way). Hope this way helpful, hopefully the others will have some bright ideas. Good luck!