Should I feel guilty?

I know some will answer my question fairly easily, if you feel guilty there is a reason. However, I'm not sure. Here's the situation:

My husband and I separated 9 months ago. We have a three year old child. We share custody 50/50 of our child. Where we each have her a few days a week, not going more than 2/3 days w/o seeing her in between. Since the separation (I left), we have both met someone. I have not introduced the person I met as my "boyfriend" to her, only as a friend. We occasionally hang out with, and do things together. We do not hold hands, kiss, etc. in front of her. I'm not sure what my husband's interaction is with his new girlfriend, but I can almost guarantee, they do not hold back. So now that you have some background, here's the issue at hand. My boyfriend's parents paid for and invited us to go to their beach cottage for a week. I do not have much money, and it is basically a free trip. The only problem is that I can't (or feel like I shouldn't) take my child. Firstly because my child is not familiar with his parents and I think would be uncomfortable being around "strangers" for an entire week. Secondly because I do not want my first vacation with him and his family to be awkward with us not being able to interact as we normally would, or to risk upsetting her that many miles away from home. And lastly because I know she would begin to miss her Dad, maybe not as much if it were just her and I, but being around others that she is not comfortable around, I think she would start to get homesick. And I guess, I should be honest here and say that this will probably be the only oportunity that my boyfriend and I will ever have to be together for an entire week, expenses paid, alone. We are both in shcool, work full time, etc.

My husband has agreed to keep her that week (of course after giving me the "you are so selfish" speech) and decided that he and his girlfriend (who between the two of them have waaaay more money than I) will take her to the beach that week. Great, I'm glad she'll be having fun! I'm not jealous at all that I'm not going to be able to take her. I took her on several day trips this summer and plan to try and get her for an entire week when I return, even though I won't be able to take off work again to take her somewhere like the beach, we can still make up for the time I didn't get to see her.

So if anyone made it through all of that....would you go? Would you feel bad the entire time (aside from missing her, because I will do that anyway). But will you feel bad in a sense that you shouldn't have gone without her, or that you are being selfish?

I worry a lot...and second guess myself a lot. I've also been through a lot the past 9 months, and even past 5 years. I haven't taken a vacation for over 7 years. I really need this and am looking forward to it...but this little place within me is saying "BAD MOMMY!!!!". Am I???