We have a similar situation in that my ILs have some definite food preferences (i.e. won't eat certain things or anything that touches them). The worst part is that MIL and FIL have different ones, so trying to find something that they will both eat reduces me to chicken breasts or spaghetti. Interestingly enough SIL is also like this but my DH has a very adventurous palette.
For them the "bad" food list includes: all seafood, mushrooms, peppers, rice, anything remotely exotic, ethnic, or "different". There is probably more but I pretty much stopped trying new recipes with them because it's a bit frustrating. We usually end up eating in restaurants most of the time they visit which I look at as a nice treat, especially since they are paying and don't visit us very often.

They also usually go "grocery shopping" for the junk food/booze that we don't have, but I make sure to send it home with them if I can. I just pack it in a bag, set it out and tell them "we won't eat it and I don't want it to get wasted".

Now I hope my ILs won't stumble across this message board!
