@rtjt,there are so many halls but it depends on your budget, actually all the suggested above by @lucky2masi,they can accommodate upto 150 persons, for regency upto 300 can hold but am sure it's abit costly, check also Sofitel Hotel, Gulf Paradise, Al Osra Near mannai round about & also Grand Regal Hotel (Towards Sanaa Signal) all these have Big Halls..