Best Friends X girlfriend

So I have this problem, and don't know what to do. I've been single now for a few weeks, and have been liking it allot. I haven't really gone on any dates, or anything.

I am in this wedding, tonight is the rehearsal dinner, ect. Tomar. is the actual wedding. I don't have a date, and have been kind of bombed out about it.

Just lastnight, I was getting gas in town, and my bestfriends X-Girlfriend (like almost a year) came up to say hi, and see how I was doing ect. She had no idea that I was single. We where always flirty with each other, and what not, but knew where our lines where and when to stop. So lastnight, we talked at the gas station for a few min, when I asked if she wanted to come over to my house? She said sure, we went to my house, and talked for a few min, when one of her friends called. Cause she had forgot she had to meet them for dinner.

So before she left, I asked if she would be my date,
She said yes, and was wondering what time we will get back, cause this wedding is out of town, by about 2 hrs
She also said that she was going to show me a really good time, and make me forget all about my X-girlfriend.

I want to, I really do, but part of me doesn't want to risk my friendship. He told me like a few days ago that I should hook up with her, cause she is great.

So I don't know what to do, I thought of just asking him again, and making sure it is ok, cause if it isn't, no girl is worth loosing a friendship over. Specially one that their prob. isn't a future with. The way she made it sound is that she doesn't want a boyfriend, but is wanting to hook up the next few nights and reall mess around, as she hasn't been with a guy since my friend. This is good, as I don't really want a GF right now, but I wouldnt mind messing around.