Re: Is there such a thing as a nice way to...
My kids see each set of their grandparents once every two weeks so I don't mind if they get junk when they're there. When we lived closer my in-laws would take the kids to McDonalds every weekend which I hated. I had my DH tell them to quit it.
Having your in-laws watch the kids is such a hard spot to be in. My mom used to watch my son when I worked part time and I always felt like I couldn't complain about little things she would do (mostly letting him watch tv) because she was giving up her time to watch my son for free.
I would send food to the in-laws and play it off as you wanted to pack lunches to make their lives easier (I did this with my mom). Or you could lie and say the kids' tummys really hurt and ask if they ate anything that could have caused it- maybe when your in-laws start naming off twinkies and ho-hos they'll realize the kids only eat junk when they're there. If you want the more forward approach have you DH tell them to cut back on the junk.
SAHM to three wonderful monsters: Tyler 6, Alli 4 and Jilly Billy 2. And all I have to say is thank God for wine!