So I booked a dummy ticket and it looks like to get the fare I would like to buy (both itineraries), the rules are:

RESERVATIONS/TICKETING RES REQ 14 DAYS BEFORE DEPART
TKTG WITHIN 1 DAY AFTER RESERVATIONS
OR AT LEAST 14 DAYS BEFORE DEPART
WHICHEVER IS EARLIER
WAITLISTING NOT PERMITTED ALL SEGMENTS
FURTHER RESTR APPLY SEE TEXT RULE
MINIMUM STAY FOR TRAVEL ON/BEFORE 19NOV 11
BEGIN TVL MON/TUE/WED/SUN RETURN AFTER 3 DAYS
AFTER DEPARTURE FROM ORIGIN
FOR TRAVEL ON/BEFORE 19NOV 11
BEGIN TVL THU/FRI RETURN FIRST
FURTHER RESTR APPLY SEE TEXT RULE
MAXIMUM STAY 30 DAYS AFTER DEPARTURE FROM ORIGIN

It looks like I need to stay 3 days at least to get this ticket, so if I fly in on a Thursday night I should be able to leave Sunday? Or Monday? And still be within the contract. I don't actually know what Delta considers "3 days".

I have flown with my kids on separate PNRs about 10 times. 4 of those times we've had irops and things have gone awry - the last time was in 2009, when we had a mech delay coming from the west coast to MSP and the kids were placed on a route via DTW, me via SEA, and my husband nonstop. We missed two potential departures because the agent helping us had a lot of trouble trying to undo what the computer had helpfully done (one kid was on an infant fare, which complicated things). I am really leery of splitting from them until they get older.