Strictly speaking, Disney's already done most of the hard work for you-- barring some sort of massive public policy reversal (unlikely) or societal collapse (probably slightly less unlikely), all you should have to do (under current copyright law) to keep something protected under US copyright law until 2108 is just not die before 2038.

Or, if you published something today as a work for hire, it'd be covered until 2103. Which isn't quite 2108, but surely Disney and their congresscritters will get you that extra five years at some point before it goes into the public domain.