Definately bring something-if his mom says that you don't need to bring a dish or anything, a nice bunch of flowers is always a good option.
Funny story about meeting the extended family-I had been dating Mr.RN about 6 or 7 months when his older brother got married. All during the rehersal dinner, and even at the reception the next day, all the family members I met ( the extended ones) asked us, will we be doing this again soon?? Are you guys next?? I knew he was going to freak out and after the wedding I was never going to see him again

. Now we've been married almost 3 years.