[rsrguy]

I use aerothane by consolidated almost exclusively.. unless I have to do a repair that was shot with dope or ranthane. I even use aerothane on spam cans as it's chemistry was redesigned in the early 2000's with flexibility as the main requirement. It's very high gloss and repairable. Many urethanes used in the auto industry just have flex agents added at the paint store in order to handle the modern bumper covers.
It would be an ideal coating for your fiberglass and foam flexi-flyer.