A lot of people celebrate birthdays at Margaritaville at CityWalk. They have lots of entertainment (stilt walkers, balloon animals, etc.), & the atmosphere is very lively. Hard Rock Cafe is probably a fun place for a party too. Neither are my favorite restaurants at Universal, but most people love them. Bubba Gump's gets good reviews too. For a unique atmosphere, Mythos in IOA can't be beat.
Sorry, I can't help with restaurants in other areas of Orlando. We always eat on property at UO or WDW. I'm sure others will chime in with recommendations.