Bonnie was there with Sirius and the twins! She probably came to help her set up as well, and would stick around to help clean up. She's apologetic that Sirius got Lucas a flying motorcycle even if it is the coolest toy ever. How do you even go about topping that? You can't.
I also don't know children at all. I'll say Bonnie got him a big swing for when they move into the backyard of the house.