I held a 1st birthday party for my son at the Aberdeen Marina's club. You don't have to be a member there in order to book the function rooms. We booked the Patio, it was an ideal room, carpetted, very bright, the patio overlooked the outdoor swimming pool. If you're not a member, you don't get to use the swimming pool, but you are allowed to use the outdoor play area in case you want to invite some older children.
There's no room fee, they just charge per head @HK$120 for the buffet and you get to choose 10 items from their menu, but the minimum charge is for 25 people.