Tumble

[myancey]

I just have each additional attacker beyond the first increase the DC by 2. Simple and elegant.

Yeah, that's a basic SRD rule for tumble as well.

Tumble at one-half speed as part of normal movement, provoking no attacks of opportunity while doing so. Failure means you provoke attacks of opportunity normally. Check separately for each opponent you move past, in the order in which you pass them (player’s choice of order in case of a tie). Each additional enemy after the first adds +2 to the Tumble DC.