You will run into this more and more with every new game release. You could as you said upgrade them to 2.0 and then downgrade them back. Some of the games can actually be played on the 1.5. Games that require the 1.51 or 1.52 update can be played using an application called "No Updater Launcher" that you can find on
www.psp-updates.com . Some 2.0 games can be played this way as well. If you search the site, I believe there is a list of what games can not be played. Star Wars BFII, Soccum,, and GTA are there for sure.
The real problem will be when games, like the upcoming EXIT, require the 2.5 update or later. Then in order to play the game you won't be able to downgrader again.
I would try and stick with 2 at 2.0 and 2 at 1.5. Then you get the best of both worlds and the kids can take turns with each game and system.
