Just a thought Hol I know you mentioned it at the start but there is a guy here in num that hires jumping castles and sumo suits etc - let me know if you need his details.
Also we went to my nieces 2nd bday on the weekend and we held it at kidstown in Mooroopna, it has everything for all ages and mini train rides etc, all the kids loved it. Google kidstown - at least you wont have to do any cleaning up etc, they have BBQ there too and on weekends there is usually a jumping castle and a huge inflatable slide thingy.