As you know, we are in the exact same position. We have never stayed at the BC/YC before (or any Epcot area resort), and chose it primarily due to SAB, as we are HUGE pool people and only spend the mornings in the parks. And we are not frequent WDW visitors -- we are looking upon this trip as our last trip for a number of years. It's so difficult when you plan so far in advance, research what is best for your family, have to plan out meals, etc, ridiculously far in advance, and then find out just weeks before you go about something like this (and not from Disney, either, but from here -- THANK YOU, TEENA! Still haven't received a letter...).
We are staying put because everyone in the family agrees it's what we want to do (well, the 5 year old doesn't get a vote

). If anyone had felt strongly about moving, we probably would have moved. But, like you, we also chose the resort for the location. We've never stayed around Epcot, and with the ages of my two older children, I thought it would be a cool thing to do. I must admit I did check BWI when I heard this news, but it was full. Not sure what I would have done if there had been rooms available. And I momentarily flirted with the idea of the Swan/Dolphin, but don't feel that can "replace" the BC in any way, shape or form (although would save us a lot of money!).
I'm taking this as a reminder to myself not to expect our vacation to be "perfect." No amount of planning can make it so, and it puts so much stress on the vacation to try to make it as "perfect" as possible. So I'm looking upon this as someone slapping me upside the head and saying, "get over it. Roll with the punches and enjoy all the things left to enjoy." Don't get me wrong -- I still am completely bummed about this SAB closure, but if my family doesn't feel strongly about moving, I think we'll deal just fine at the BC.
Like you, we have been smacked around a bit by life in recent years (heck, as I'm learning more and more, who hasn't?). The last time we were in Disney (two years ago) my youngest daughter had a gastric tube, was on morphine and chemotherapy meds on a daily basis, and was unable to deal with more than a couple of hours in the park at a time (and was often in pain/nauseated when there). Now we are returning for her, so she can enjoy it a bit more after surviving over two years of cancer treatments. It's so hard when you've been through things like you and we have to not put a lot of pressure on your vacation plans to be "just so." We all want to leave the stresses and fears we've been dealing with in our daily lives behind and totally escape. And when part of that "escape" relied on afternoons enjoying SAB, well, the disappointment is huge. The trick is for your family and mine to just redefine our "escapes" now that we are armed with this information (and again, thank goodness we have it -- THANK YOU TEENA! -- because it allows us this time to regroup and figure out how best to work around it). How do you want to redefine it for your family? Can you come up with a BC plan that lessens the emphasis on pool time and compensates for it more with something else the BC can offer (other activities, more Epcot time, etc)? Or is the pool time such an integral part of your escape that it truly would be best for you to stay at the Poly? (Which is a wonderful resort, and fairly convenient to Epcot too). Will DH be unhappy if you stay at the BC, and is it worth it then to switch back?
It's a difficult choice. And made more so because I think families like yours and mine may feel even that much more pressure to make this a fabulous escape. I personally think you can't go wrong at the Poly. And perhaps you can't at the BC either, but you need to make sure that everyone in your family is on board and ready to deal with the SAB partial closure if you switch back.
Good luck with your decision. I'm sure you will have a great vacation regardless!