Dr Midnight said:
That'd be faboo, except I'm the ONLY guy I've ever known who just isn't interested in the menage. Seriously... just doesn't do anything for me.
Just talked to Alison (who talks on a cell phone whilst working in a kitchen at a local restaurant), I've taken the advice of y'allses and am going. We're on for 6:45 this Thursday with her sister at D&B's in Providence. Since her sister is a graphic designer, I'll at least have something in common with her to talk about. Man, I hope I'm not setting myself up for a stiletto to the gut here...
Fabulous, doc! For a second, there, reading the responses here. I thought you were going to shirk the test!
I'll give one piece of advice here, and then I'll do something spectacular - I'll quit giving comments from the peanut gallery altogether!
BE YOURSELF, just as you were on the first date. Some people think being yourself means scratching your armpits in company, but I'm not talking THAT much yourself.

Seriously, unless given a proven reason otherwise, take her moves at face value. Like someone else here said, the true test of a worthwhile person to spend time with, whether for romantic reasons or no, is that you can hang out with them. That they don't have to be "on" all the time. Plus, whether the date goes well or not, you are at Dave & Busters! THat place is FUN!
Finally, think about this: you two met because of a personals ad. DO you know how many people don't like personals ads, because of the number of "freaks" who post to them (present company excluded)? She might want assurance that you are as "good" and "healthy" as she thinks you are!

After some of the realitons you have been through, you could be as much of a "breath of fresh air" as she is for you!
I don't know if you think she could mean something long term, but don't think about it (which it looks like you are not, which is good) - every relationship is taken day by day. One day you are hanging with her sister, and the next day - who knows?
One last word: My wife, when we were dating, took her 9-year-sister with us on an "outing" - that was MY test. It was to see how well I could act around her. 11 years later, I love her to death and kinda think of her like a daughter myself.
Anyway, good luck, and don't be Don Juan - be Doc. You're smoother, anyway!
P.S. - I know what you mean. Who in the he** ever postulated that all hetero men are into threesome's anyway?