I would NOT try to transport an adult goose in a cardboard box. I've never tried putting one in a box but as fast as they peel bark off trees and destroy various things, I think you could very probably have a loose goose in under an hour. WAY under an hour.
What about making a cage out of 2x6s for the frame and hardware cloth or possibly chicken wire for the sides? I've never kept a goose in chicken wire, so I'm not sure the regular type is sturdy enough.
Oh, and you MAY find he is fine with your goslings at a very young age, so he may not be alone so long. In fact, the introductions could go much better if they are babies.
My ganders are all fantastic with babies, even not having been around for the goose setting.
Edited to add: I think if I did make a cage like that for transport, I'd plan to protect him from sun and wind with a tarp or something.