I don't see how the math works for buying direct for three people for 2042. Even if they bring back the AP discount (big if!) you have to lock all of you into APs for 20 years and even then I don't think it works. It didn't for my family when I crunched it over the years. And I don't expect my teenager to have any interest in getting 9 WDW park days in 13 years from now.
I guess I can make this argument better for OKW, assuming your kid and their kids will be grandfathered into Blue Card (also a huge IF). But if that is what you are going for, I'd pay a little more for BLT or newer. Even Riviera, and I'm a never-RIV.
If Poly is what you love, and what you plan to keep, I might even consider Poly direct. The contract length matters when you are talking about passing your contract and your Blue Card down. If this is based on FOMO, keep in mind there is no new resort and there won't be for many years at this rate. I'm sure
DVC will be happy to take your money then if that resort ever happens. If this is based on AP discounts, then you need to do the math and really consider the risk you are taking with a lot of money.
It's worth noting that they could completely get rid of Blue Card or change the rules on gratuitous transfers and all that. RIV has made it very clear who it benefits when they start changing the rules.