If they're southern California residents - they can get the Costco Play 4 Days deal. It's entrance to one park (either DL or DCA) on 4 separate days, for just $129. You can't park hop, even if you want to use up 2 "days" (e.g. 1 day for DL and 1 day for DCA, on the same day).
There are no black out dates, no time limit, except that the last ticket has to be used before November 16, 2007 (well, I mean, that's the last day you can use the tickets). It's not like the multi-day park-hopper, where the tickets have to be used within 13 days.
The tickets can be purchased at Costco locations in Southern California and online - if you don't have a membership to Costco (which is like $50 a year), you would have to pay an extra 5% on the tickets.
The downside is that you have to take the voucher which you get from Costco to the ticket booth and get a one-day ticket each time. (If you purchase at Costco, you pick up a plastic package thing and pay for it, and then take it to the merchandise pick-up and exchange the plastic thing for the voucher - which you then take to the ticket booth at DL... a bit complicated, but for me, the savings are worth it!)
They check for SoCal residency (either with driver's license or i.d. card)... I think someone suggested maybe asking someone else to trade in the tickets (e.g. if your friends don't have a driver's license or id, showing southern CA residency), but I don't know...