We are also doing a split stay on an upcoming trip of 11 days (1 day GF/7 days BC/3 BW) and I initially booked the dining plan for the BC portion of our trip, which meant we'd be paying OOP for all GF/BW day meals. Initially, we booked it this way because we also think it's too much food and didn't want to be on the plan for the entire duration of our trip. We also have BW booked as CL, so we wanted an opportunity to compare costs to get an idea of whether it might be worth it for us to do CL in the future (e.g., if it saves us a little money on dining).
However, in the end, we decided to upgrade my 10 day WP&M hopper ticket to an AP (with the intent to use it again later this year for a few days), get the TIW card and just not do the dining plan at all. I also looked through all of the menus, added up what we'd be buying vs. what we'd spend if we had the DDP, and the TiW card offers me at least a $300 savings (and that's taking into account the $100 I need to spend to buy the card). If you don't intend to return to Disney within the year, though, you really need to sit down and run the numbers a little more closely: I'm paying about $180 to upgrade my ticket to an AP + buying the card, so if the TIW card doesn't offer you more than $300 in savings over the DDP, it's probably not worth it to go that route.