The original expiration date for OKW is 2042. Owners were offered an opportunity to purchase and extension until 2057. Some did, many did not extend. Disney only sells points with the extended expiration of 2057. For resale contracts it all depends on whether or not the contract for sale includes the extension. Some do, many do not. The extension is no longer for sale by Disney.
All contracts are extended, the only question is who owns the extension, Disney or another owner. You can find 2057 contracts resale and they may be the best deal. I've seen a couple of reports of resale buyers being able to extend around the time of purchase but it was postulated that the owner had never signed over the extension to Disney. I suspect if one wanted to they could get Disney to sign over the extension for the $25 fee.
For listings it'll say if it's 2057 but it doesn't hurt to ask. I personally have a concern about owning after 2042 since only roughly half at most will be owned by members and the other half or over by DVD. What will they do, how will they handle it, will they pass on the management just to the other owners? Will they use it for college housing? Will they reduce the size of the resort and thus increase fees? If you want longer you can buy something else that will do better like SSR or AKV IMO. They may offer other extension for the rest of the resorts but OKW has made their bed and not in a good way. Is it a major issue no, but it is an avoidable one for new members.
For that situation I think you have several good choices. First SSR 2 BR isn't that much more than an AKV 1 BR. And the AKV 2 BR value is little more than a SSR 1 BR though value is difficult to reserve at times. The AKV 1 BR Kidani (and BLT) has the second bath and pullout chair. IF you prefer to stay at AKV, I'd likely buy there. Realize there will come a time when you'll need a 2 BR regardless at least for a few years. Plus you can still reserve OKW fairly easily with non OKW points if you want. And getting in to AKV for a 1 BR at 7 months out isn't the difficult. Ignoring personal preferences and just looking at sleeping and cost with a long term view SSR will still likely be the cheapest and do everything you need but AKV will offer other options and COULD be cheaper depending on how you play it. BLT won't be all that far behind, esp if you buy there and use the points at the other places part of the time. As for AKV dues, they are on the high side and likely to rise slightly faster than SSR or BLT IMO but not enough to be a deal breaker or make you have to sell later just for that reason. I'd personally go with SSR because it's cheaper and other than AKV value, should do everything you've mentioned here but it may be more hassle if you want to be elsewhere at 7 months out much of the time and you have to weigh those options and risks. I don't know how old the boys are but if they're old enough for it to matter now you'll likely only have 10 years or so with everyone going for the 5 total. After that you may lose one or more for given trips and the 1 BR anywhere will work or you may pick up a couple of friends and you'll have to get the 2 BR anyway. Just educate yourself, then if DVC makes sense anyway, take your best shot and see how it goes. It's not a permanent choice if it's a bad one.
And that's the best because you have to decide what's best for you and your situation. Sufficient time, knowledge and experience will answer these questions for you though some uncertainty would be normal unless you have a ton of experience and thus give up some savings. There's a sweet spot of knowledge, DVC and on property experience to make good decisions but not give up too much savings. IMO 2 of the most common mistakes people make is not buying when DVC does make sense or buying too quickly before they've garnered sufficient knowledge. That's esp true when they're trying to get that next trip on points to kickstart their savings.
