The problems with planning...

So I was talking to one of the guys I've met here, he's from Houston.  He told me he wanted to go to Auschwitz this weekend, and I really want to go so I said I'd go.  Then I asked my chief if he wanted to go, and he said yes.  Today I confirmed with my chief and he said he didn't want to go anymore.  I decided then that I'm going anyway.  I wanted to go to Auschwitz and Krakow.  Of course, a few hours later I get a call from the other guy from Houston, and he wants to know if I still want to go.  He said he thinks he has Saturday off but he's not sure about Sunday.  And I really wanted to spend the whole weekend down south.


Do I change my plans for this guy because he wants to go?  Or do I just go with my original plans?  I mean it isn't a huge deal if I only go to Auschwitz.  I can go to Krakow another weekend.  I just don't want to rearrange my plans and then the whole thing falls through.  Then I'm stuck in Plock - again.