In Oshiwara, Andheri, Raheja Classique Club is a good option if you’re looking to throw a pool party, as it is a private club and has a big lagoon-shaped swimming pool. Although it like most clubs requires membership, you can as a non-member rent out its facilities with the reference of a member {which they can help you to get}. You have to pay for the catering and ask for pool services separately, which isn’t exorbitant.
For snacks, it costs somewhere around INR 650 per plate, {plus taxes}, and the swimming rentals are close to INR 220 per adult. You can contact them for details at 022 6695 5550.