I am planning to use the Ahnentafel numbering system, starting with myself. After all, I *am* the one doing the research, regardless of my own children.
Then I will (separately) number THEM with a descending system, allowing any of them or their future descendents to track how they connect to "individual #1" (me), and thus figure out how they fit into the ascending system.
I don't know if that's the ideal solution, but it makes sense to me.