No Kid Drama

Okay ladies, tell me if I'm crazy or if I have the right to feel the way I do. My fiance's parents are guardians of his 4yo nephew, and will be traveling about 6 hours to our wedding. We have a strict no kid policy for the wedding, but his mom is insisting on bringing his nephew to the wedding. She said if we don't want him there then we need to find a babysitter for them to screen, which obviously works in their favor because they never visit us and would never have a chance to meet the babysitter beforehand. I have so much built up anger and resentment about this whole situation. Anyone I know and trust is already invited to the wedding. I hate to run the risk of them deciding last minute that they don't approve of the sitter, and then the child will be around while I'm getting ready, through the rehearsal dinner, the ceremony, and reception. They keep threatening that they just won't come if we don't find them a sitter. Oh, also the sitter has to be CPR certified and have at least a 4yr degree in early childhood education. I would love some advice.