DD2 went to a Build a Bear party at the Mall and loved it. She did say that it wasn't a real party because there wasn't cake or the birthday song.
Perhaps ask the coffee cart outside the Mac1 around the corner if you can use their little seating area for the cake. Shout the parents all a coffee from the cart (tell the cart you will be buying 8+ coffees if you can use their seats) and have the song and cake cutting. There are 2 bins nearby and cleanup is a breeze!
If the cake isn't possible perhaps partybags or individual cupcakes in boxes from that cupcake place outside Woolworths? They would be easy to hand out after singing the happy birthday song in the bear shop.