I had exactly the same situation with my PFB years ago now. EBF, and hen do booked for four months long before delivery. I naively thought it would be fine.
It was for two nights (so not quite as long) a good four hours travel time away in a different part of the country.
When it came down to it, I knew I couldn't stay the whole two nights and opted for one. I took my pump, and aimed to pump every three hours or so.
In reality - I didn't miss her as much as I thought, but that's not to say I didn't miss her because I did loads! But I wasn't inconsolable with grief or anything and it was lovely to be "me" again with my friends. For a FF mother, I'd definitely say go for it!
However, the breastfeeding side of it.. my good intentions even with one night away soon slipped over every three hours. With hindsight and the amount she was feeding (on demand feeding whenever she felt like it!) the sudden shift to scheduled several hours gaps was not what my supply was used to. I'd also easily get distracted with friends (especially in the evenings after a few drinks) and I went longer between pumps than intended. Three hours became four on several occasions, and without a baby to wake me that night I was happy going for five hours, something DC1 had never done. Trying to find somewhere to plug in my pump (and when back at the "base" the walls being thin so I knew I was disturbing the other hens) got awkward as well.
I kept and refrigerated/coolboxed all the milk I collected for the 36 hours I was away, and it was probably under half of what she'd consumed back home.
After I got home it was clear that even with a 36 hour break with pumping that my supply had taken a massive hit. My breasts felt soft when she was starving, and it took a good few days of basically doing nothing except letting her suck constantly before things started getting back to normal.
And I thought I responded well to the pump.. I guess when it's a pump to replace a baby, not as well as I thought. I later pumped at work from 4.5 months until 12 months and often had to do extra pumps to make up enough for the next day.
That's not to say this will happen to you, because one thing I have learned (am on DC4 now!) from all the due date groups I've been on is that women are all different when it comes to their milk supply and how they respond to pumping etc. But I never spent a night away from an EBF baby again.
That's also not to say I think you shouldn't go. If I were in your shoes based on my experiences, I like the suggestions about DH staying nearby and bringing baby over/you visiting as well as the odd pumping session when it's not appropriate. Or going for fewer days.