My wife plans too many outings/gatherings with her family?

My wife and I have been married five years. During this time, she seems to want to do nothing but "family stuff" -- her family insists on having a gathering for every conceivable occasion, it seems. Everyone's birthday (including five nieces and nephews, two sisters and brothers-in-law), Christmas, Easter, Thanksgiving, trick-or-treat, are all included, plus she wants to spend a lot of time at her parent's yacht club (this really isn't my thing). She expects me to go to these things or she gets upset. Is it reasonable for me to ask her to back off a little from all this "family" time?