Wow - advice all over the board. I feel bad about suggestions to not bring baby. I have avoided weddings where children are not welcome, myself. Totally their day, their event, etc - and I understand that - but my life is my children, and I chose to leave my professional job to stay home with them - and bring them everywhere with us, as a family. They've not needed an overnight sitter - as a choice by our family values. That said, I do take our children to weddings and funerals, albeit appropriate. I don't walk my children up for a viewing, unless it's a dear family member, etc. And as for weddings, I am courteous enough to step out if baby or child fusses. Perhaps it's because my children attend church with us and attend weddings with us, they are appropriately behaved and do not detract from the wedding.
'k, off my my soapbox. Sorry.
As for bringing your breastpump - absolutely carry it on, if you feel you need it at all. If you use it now - definitely carry it on. I owned one and used it a handful of times as I worked the first year of my first child's life. Only when away from him, etc.
And I loved the post about extra dipes and wipes and clothes! We traveled by vehicle from ND to CA a few years ago with two kids, ages 4 1/2 and 2. We had planned stops for laundering - but things happen. I tripled the number of outfits per day, just in case - and many of those were sleepers or jammies, etc - just for comfort and ease of changing, smaller size to pack, etc.
Good luck and have fun!
T.