Other than the dilated pupils, MDMA is one of the easiest drugs for me to hide as long as the dose is under 170 mg or so. At 170 mg or under, I don't get bad eye wiggles or a messed up face or anything like that. I find MDMA easy to bring under control if I need to. In high school, I took some on a class trip to six flags and I talked to several teachers through out the day without any of them noticing anything. When I'm rolling, I can usually manage to think pretty fast. When I'm drunk, high on weed, or tripping, I have a hard time thinking fast enough not to sound retarded. With MDMA, it's never a problem.
As for taking it at a wedding, I'd say go for it as long as you keep the dose low. Since other people will probably be drinking, a low dose will leave you way more functional than most of the drinkers. Just don't take so much that it's clear to everyone that you're on drugs. A low dose of MDMA will make you happy, and weddings are supposed to be happy events so you'll fit right in. If you were going to a funeral or something, I'd say that rolling would be inappropriate.