Years ago I had to draw the line in the sand with my mother...it wasn't pretty and landed me in therapy, seriously. When I got married and moved out of state my mother felt that it was our responsibility to travel home for all the major holidays. For several years we packed up kids and all of their assorted giant, little tikes, plastic craptastic gifts and hauled ourselves back to that state at her wishes for the holidays. For awhile it was fun...until it wasn't.
Finally, one year I tried to hint that we weren't coming, I realize now that it was immature of me, I should have just come right out with it from the beginning, and said we weren't doing it anymore, but my mother, and worse, my father, hold grudges. When I finally was exasperated and said straight out we weren't coming, my father had a few ridiculous choice words for me. Also immature behavior on his part.
I ended up in therapy for a few months learning how to set appropriate boundaries that my old school Italian mother had no choice but to respect. It has been much smoother sailing since then.
I suspect that at some point your wife will also have had enough of her family failing to respect boundaries and will put down her foot. Unfortunately, until that happens, your choices are limited. Try to make sure plans are outlined and agreed upon way in advance. Your wife really has to want to address this with her family. That's probably the discussion you should be having right now.
