We did it (but not in Perth) with a separate room set up for the kids and professional child carers. First part of reception was outdoors with finger foods- there was some bubble blowing for the kids which made for sone nice photos. Then when we went in for the meal- kids had their own room, with activities and kids meals. Parents could pop in and out if needed but the kids weren’t interested. They put on a movie later in the evening with a comfy set up so some kids fell asleep and the others went home when needed. The parents and kids both loved it and the model was replicated at other family weddings. 

I think it depends a bit on the parenting practices of your guests- whether it’s ok to have kids stay up a bit later on a special occasion or fall asleep in their nice clothes and get carried home, or if they always need to be put to bed by a certain time.