honestly - going sounds like a nightmare, I wouldn't (well I wouldn't now, but I probably would have done in the past and regretted nearly all of it) - but it's not my decision
it's nearly 4 months away and you're stressing about whether to go, whilst away on your peaceful break. i know thinking about these things can sometimes help to crystalise our thoughts and feelings about bigger matters, but do you have to decide now?
When I was with (now x)AH I would often worry myself silly about things that seemed tiny or simple to people not living in my situation, I would play out all possible scenarios and the consequences that would have, how he would behave, how I would feel. I was trying to make a decisiona bout a small thing but my decision making procedure was being buffetted and overwhelmed by all the big problems that impacted on this little decision but that I was avoiding.
Objectively whether or not you go on a 4 day trip is not a big decision:
taking into account everything you know about how it will be based on past experience, will you be able to fully enjoy yourself, or will you be dissapointed/angry/upset/uncomfortable and end up with more resentments?
Nor in most relationships would it have major ramifications, the fact that it feels like a big decision, and you worry it will have big consequences, probably tells you lots of things about the bigger picture things that are going on.
which is a lot to deal with, so,
IF he brings it up, you could always say you haven't decided ('cos you haven't) until it becomes clearer for you?