So I have a serious dilemma right now.
I'm starting a new job at my uni this semester and I'm really looking forward to it because a)it's interesting work that's connected with my studies, b) it will look really good on my CV and c) it pays relatively well (and everyone who's in an LDR knows how important that is). Oh and I will have half an office on the campus and work on campus, so that's a major +, too.
The thing is... I haven't even started yet and already have the first problem:
My prof just wrote us an e-mail that theres going to be a workshop the 2nd weekend in June. I'm going to be at my boyfriend's. I already have the tickets. He had mentioned that workshop and that it'll be a weekend in June, before. But I figured that... there's four weekends in June and this one is a long one (Monday is a holiday - Pentecost), so like everybody is going to be out of town anyway. Chances that it'll be exactly that weekend are small, right?? RIGHT?!

I really have no idea what I'm going to do now.
I don't want a bad start at the job and that workshop is going to be super interesting, with experts for 8 slavic languages coming and what not. I want to be there. I really do and I don't want to diassapoint my prof.
But... I already have the tickets. If I gave them back, they'd only refund me 50%. It's basically the only weekend in June that I can see my boyfriend, because he has exams later that month. I checked prices for the earlier weekend, but trains are about 130€ and flights 150€ (+30€ I'd have to pay for the tickets I already have anyway). Too expensive - can't afford.
Plus it means we probably wouldn't see each other for over a month, because he might or might not come to visit me in the end of June and the next time I'm visiting him is July.
I know for some of you that might not be a long time, but I can't and don't want to do it.

Also... when is the best time to tell my prof?
We have a meeting in the beginning of May, where he will tell us more about the project/workshop. So I could bring it up then. Or send him an e-mail... like now. But it's probably better to bring this up face-to-face...is it?

*edit: The girl I'm going to work with has just sent me an e-mail asking about the weekend (we were supposed to officially start working in July/August and are both somewhat confused about June and everything) . I think we can figure out something together once I get back to Germany and then do something about it together. I feel a lot better knowing I'm not in this alone.