Honestly, I'd consider the very real possibility that you and your nephews are gonna have to share a 1BR. If that sounds like it might be a burden, OR if you also have kids that would make including your nephews exceed the occupancy of a 1BR, (I don't know if you have kids or not, sorry), then I'd say you might be setting yourself up for disappointment.
I can't remember if there are cancellation fees for people who book rooms at non-DVC resorts that then have to cancel. If there isn't a cancellation fee, I'd suggest booking two adjoining rooms in any resort where there are still adjoining rooms to be had. If, by the time you're close to 30 days before your trip, they still don't have a two-bedroom, cancel the DVC room, bank the points, and use the other rooms you booked. And if you can get the two-bedroom, cancel the other rooms, & consider the one-night deposit that held the rooms for you "found" Disney Dollars. Either way, have a contingency plan.