If money is tight then I would stick with the Bike Friday. A loaded down bike on tour is a different animal from a racing bike. You ride it differently, it feels differently. I actually like a loaded bike. Your young, a few extra pounds aren't going to make a lot of difference. I haven't tried the case as trailer. You could always store the trailer and just use panniers. Picking out a tour bike is much easier after you have done some touring.I'm beginning to think this is the best solution if money is tight and the model Bike Friday you have is suitable for racks and panniers. I've ridden a Bike Friday a modest amount (my son-in-law has one) and, while it's initial handling is different from a 700c wheel bike, you get used to it pretty quickly. After that, it's just another bike and only seems strange when you look down.
+1. For several years I did a bike-train-bike commute on a Friday New World Tourist. It was actually geared too low for my relatively flat commute. Many years ago I spent a week off and on touring with a couple riding a Friday tandem pulling the suitcae trailer you describe. Don't recall the model, but it had drop bars. Whatever model it was, they managed to drop me for a bit climbing Hoosier Pass from Breckenridge, CO and had no problem on the descent to Fairplay, where we went our separate ways.
As for airline bike charges, last year U.S. Airways from Philly to Venice was supposed set me back $200 each way. Fortunately, the rent-a-agent who helped me with the kiosk check in didn't realize one of my checked pieces was a bike (or didn;t know there was an extra charge) so I only paid $100 for it as my second checked bag (the first was free). But they got their $200 for the flight home.