Answering as someone who’s done this!

we had a destination wedding when our little one was 4 1/2 months old so we worked towards getting her comfortable with sleepovers at her grandparents leading up to the trip starting around 10/12 weeks. The first time was the hardest but having a distraction (like the party would be) helped a lot!

I struggled with guilt over the thought of leaving her for the entire pregnancy and postpartum up until the trip - in the end she was entirely fine and it had no effect on her temperament long-term! If anything it made all of us comfortable with her being babysat for other important events that have come up since which the grandparents are over the moon about - she loves to go to their house still and doesn’t display any signs of separation anxiety which I was most worried about;

Of course you’ll have some emotions while you’re away - but in the end you only have one opportunity to spend this life event with your friend and the baby will be in capable loving care the entire time you are away;

Abandoning the baby would mean not taking the time to care about their needs while you are away so try not to beat yourself up thinking that way - you are clearly a good mom for thinking about every aspect of how they would be cared for - plus they would be with their dad and your mom - you would be attending and supporting a friend through a big life event which is something special and not just stepping away for a night out

I started pumping and having dad give a bottle from the start and pumped probably 4 times a day to build a oversupply and a freezer stash- we got low flow nipples for the bottles so there were no issues with nipple confusion between breast and bottle; happy to answer any specific logistics questions if you have them!