My most exciting most recent find has definitely been Don Bosco at St Marys. I was aware of how great it is for parties, but for some reason I only recently became aware of their free open sessions. You can check for times on their website here. Just make sure you check the times and ages, most of their sessions are aimed at kids over 10 years of age which I think is great, our teenagers do not have enough safe free activities to access.
I frequently take my kids to the under 10s sessions though, and as well as being indoors the bathrooms are super clean, and they are happy for you to bring in your own food. There is a canteen there but you really need gold coins to access it, there is also bubbler with water. They have trampolines, pool tables, foosball, pingpong tables and soccer, basketball and volleyball facilities. There are usually some balls floating around, and the pool tables/ping pong etc. all have the paddles and balls and cues that they need to be played. There is seating all up the southern side of the building for parents to sit while kids play.
They have a free session for under 10s every Saturday morning from 10am until 11:30am, honestly this is my new go to for play dates with school friends. There are different (more) times for school holidays, and different times for over 10s. The first week of school term, the week of Christmas/New Years, and the first three weeks of Term 1 they are closed. Don’t try and park next to Don Bosco in their parking lot though, it is tiny, it is hard (and dangerous) to try and get back out onto Mamre Road, and you have to walk around the entire building to enter. Go to the next driveway which is the entry to the Council halls and park there.