If you bought new machines, you can kiss PM good-bye. Beyond Windows XP PM is nothing but a crapshoot and will likely not even install.
Yes, I advise keeping the old computers (or some of them) for the sole purpose of running PageMaker. And plan an exit strategy, it is dead.
If I recall correctly I never deactivated Pagemaker. It blew up occasionally and I would just reinstall, never re-registering. But all the above advice still applies.