I've been thinking about this post/thread longer than I care to admit. Here we go OP.
You've got a young family with young children.
DVC is a long-term investment. Your family values resort pool time. But there's practicalities in this that can't be ignored. You've got a family of 5 (maybe expanding, I'm not going to purport to know your situation). While Poly is nice, the rooms alone prevent it from being a viable option for your family vacations.
SAB at BCV is great, nobody denies it. But that 2042 expiration and price point simply don't make it a practical choice for your family who wants both short-term value with small children (too big to keep track of all the kids) and long-term value for your money.
Therefore, I think you have 3 real options: VGF, WL, and SSR. All three of these have enough room options for family of your size to be viable. Additionally, the rooms at these 3 are all on the newer side (VGF and BRV could use an update, CCV is pretty new, and SSR obviously newer than the others due to the recent refurb). My thoughts below. For the record, we own at VGF, CCV, and Poly.
1) VGF. I think VGF provides the most immediate enjoyment for your family. The splash pad is well-designed, whimsical, and there's something magical about staying at the Grand Floridian with the monorail and now walking access to MK. That said, the
point chart is steep (and we own at VGF). There is some concern that the kids may not want the ultra-intense theming
disney vacations of a monorail resort as they get older (odds are that at least 1 of your 3 future tweens and teens will have a "anti-Disney" phase), so burnout is a real possibility.
2) WL (CCV or BRV). I think WL provides a better balance for both short-term and long-term return than VGF with your values (and the point chart is more favorable). The pool area is definitely more suited to younger children, but has more room to grow than VGF (my opinion...fwiw). The boat ride to MK never gets old, and the theming is remarkable. Good food options and nice rooms. Can't go wrong here. WL can feel like a vacation within a vacation, so I'd be less concerned about burnout than with VGF.
3) SSR. I think SSR would suit all your needs perfectly and I view it kind of like your insurance policy. First, the
point charts are phenomenal for SSR. Second, SSR has great pools for both small children and all others. Third, odds are that at some point, you'll have a child go through a "I don't like Disney" phase. When this phase hits, the proximity of SSR to Disney Springs is going to be incredible. I think SSR is the most underrated resort on Disney property and if I were you, with your family size and values, I would buy here.