Jaime, I don't know if you'll have time to read this before you leave. First of all CONGRATULATIONS!!!! That's just awesome.
What to wear I would try to wear solids, I know that white, tans and blacks photographed the best. If they take full body shots, you can lean on one side a bit and put your arms around your waist, it'll make you look slimmer.
Other than that, just smile away and have fun with it. I'll have to come by and check out your new gallery. Where is it going to be?