One plus to having brothers and sister(s) is that there is always someone to play with. If you can't do something, there is someone who can help.
The trailer and trike with Ben above was the standard play item and Mimi and Granddaddy's recently. Hook the trailer up, ride around, load the trailer, unload the trailer, etc. etc.
But that's not good enough for my children. Where's the challenge in that?
Why make do with a dinky pedal tractor trailer when you can pull out the big boy?!?