All grown up

So, I keep meaning to tell you!
Joe and I are doing something mature, and grown up and terrifying. We have a play/dinner date with another couple our age with two boys that are both within a few months of Caleb and Jack.

I've know the husband J, for about 7 years, and his wife J, almost as long, though I was never really friends with her. He and I worked together for a few years, which was how we met. Even though he was my boss he's only four days older than me and we always clicked really well. Too well, in that there was always an inappropriate tension and I am sure people thought there were things going on. They never were, but any time a male and female are friends the rumors abound. I think it was part of the reason I was never completely comfortable around his wife, that I was always afraid if she wondered too.

We had a bad falling out several years ago, as things will happen when you work with someone you are really close to, and since I quit at this time we never really hung out again. I've sort of kept in touch, every few months I'll call and say hi, or whatever. Anyway, it occurred to me, here's a married couple our age, with children the same age as ours, who I've got some prior connection to, why not see if they can be our "couple friends"?

I called last week and ran the idea by him, and then she called a couple of days later to set the date, so now we have this whole grown up dinner date planned. I feel like I should take something, she said no, but it seems like the right thing to do. The problem being that my only ideas are things I see people do on TV. Wine? Chocolates? What to grownups bring other grownups for dinner at their house? And Jesus, does this mean I am now one of those grownups? The thought really frightens the hell out me. I mean, you read me, I'm not remotely mature.

Help me internet! How do I play dress up for the night and pull this off?