My family likes to play games. Team games or get to know you games can be a lot of fun, and if both sides of the family don't know each other well, it sparks conversation and laughter, and fills in the lulls. Some of our favs are Dirty Minds, Trivial Pursuit (teams so no one feels 'dumb'), Battle of the Sexes. Thanksgiving, we played Match Mate (sorta like the newlywed game) - it's for couples only -- and could be TMI for your parents, depending on your relationship with them. The games I listed are all playable by hearing impaired. My dad is deaf, and a surprising number of games don't work well for that. However, he can read the questions from the cards on these, and all have individual responses or concensus rather than lots of shouting out.
Serving drinks that appeal to everyone can break the ice well, too. We serve beer, wine, something fruity, and lots of snacks :)
My family is also going to a turkey shoot (surprisingly fun - you shoot a target, not a turkey, with shot, and the the target with the hole closest to the center wins --- you don't have to be the best shot, you just have to get lucky with one of the pellets). It's an annual event for us, and is a fundraiser where we go.