Dropping kids off at birthday parties. OK or not? | Parenting

I have a 16-year-old, 14-year-old and now my youngest is 12. So, I've pretty much been through a lot of the 'stages' and thresholds of kids gaining a little independence. But, I'm still at odds with myself over whether/when it's OK to drop my youngest off at a birthday party without me attending.  (How did my handle my other two? I always seemed to know the families, strangely enough.)

My daughter came home with an invite the other day. Now that she's entered middle school she loves her friends and the new possibilities that come with a larger social circle. For her, she is thrilled to be invited but none of the other partygoers' parents are staying. I don't really know the birthday girl's family, but I know people who know them.  They are known to be a wonderful family-- and it's a daytime birthday party.

I'm going for it and letting her go.  I will walk her in and meet everyone, but I still struggle with new boundaries.  What do you think?

• Is it OK to let her go?
• What questions do you ask  before agreeing to an event that you will not attend?
• At what age do you ask about whether it will be a co-ed affair...and at what age is that ok?

Let me know what you think.... Party on!