I take DS to Gymbaree (im not in Oz but am sure it is the same, only the american version). DS loves it. The first time he was there was amazing, the look on his face, he had all this room to move around and not be told "dont touch". We go to movement classes 10-18mths and basically, there are activities set up and we just move around from activity to activity. Basically, we just follow the kids lead, but at the same time encouraging them to ie, climb or go through the tunnel. There are also a couple of group activities. Each week is a different theme, ie, rocking, climbing.

I dont think 7mths is too young. If he is crawling around or even trying, it could be encouraging for him. We were able to have a free trial class, maybe ring and see if you can have a trial class first and then decide.