I've done split stays before, with the 2-day ticket requirements. Taken literally, the idea of using one set of 2-day tickets for the first reservation, then the second set of 2-day tickets for the second reservation, makes your ticket expenditure high.
(prices don't include 6.5% tax)
(1st Reservation) 2-day tickets upgraded to 3-day tickets = $232 each
(2nd Reservation) 2-day tickets upgraded to 3-day tickets = $232 each
Total for 6-day tickets per person: $464
Here's a better plan
(1st Reservation) 2-day tickets upgraded to 6-day tickets = $259 each
(2nd Reservation) 2-day tickets, unused, to take home for next trip = $168 each
Total for 6-day tickets per person: $259
Bonus: You have prepaid 2-day tickets to apply to next trip, or sell outright.
The first 4 days of a MYW ticket are the most expensively priced. After 4 days, park days only cost $8+tax each, up to max 10 days. So, it's cheaper to upgrade your first set of tickets for your whole trip, and take the second set of tickets home. Unused MYW tickets never expire, and are completely transferable. You can ask the Concierge desk to remove your 2nd set of tickets from your 2nd KTTW cards, and place the tickets on separate cards. Put these cards in an envelope or baggie and label them.
To learn more, and to see current ticket pricing (Post #18), see Cheshire Figment's Ticket Sticky, "Everything About WDW Tickets."
http://www.disboards.com/showthread.php?t=1452684