We did the same thing for our last trip - borrowed in-laws' RCI Weeks account - and ended up getting a 1 bedroom at Boardwalk. The in-laws' timeshare is at a decent resort in Puerto Vallarta, but it's not super huge and there is a lot of inventory in Mexico, so we had to combine 2 weeks to make sure we would have enough TPUs (if you need to do this and the in-laws have to deposit their 2016 week, they would have to pay those maintenance fees to their home resort before it can be deposited with RCI, so that's another hurdle to jump over). So if you aren't going to have enough TPUs with just one week (assuming the in-laws have a weeks account) that is another fee to combine weeks. I think between the exchange fee, the combine fee, guest certificate and resort fee at the hotel, we ended up paying $400-$500 for the exchange, which was a steal for a whole week at the Boardwalk!
I spent a lot of time on the various timeshare boards about a year in advance to figure out all the details of trading into
DVC, and here are some things to remember:
What you see in just the open exchange inventory - not just DVC but pretty much any property - on the RCI website is essentially just leftovers that didn't match up to any ongoing searches that have already been set up. Anything that does make it into open inventory gets snapped up pretty fast, so getting an ongoing search set up is crucial.
The DVC units are usually deposited into RCI about 5-7 months out, give or take a few weeks, though they do occasionally have last minute deposits for travel dates within a couple of weeks. But, you probably want to have your ongoing search set up at least a few months before that 5-7 month window. I think we had both weeks deposited and combined and the ongoing search set up by April or May 2013, and we had our match during the first few days of August 2013, so we were matched about 5-6 months in advance for a trip the last week of January 2014.
I had been monitoring RCI for several months before we got our match and it looked like for all but the holiday weeks, the 1 bedrooms were going for 20 TPU or so. I would check inventory several times a day and I regularly saw SSR units pop up as well as the occasional AKL, Wilderness, Boardwalk, and I think maybe a BLT once (?). I think our exchange was 22 or 23 TPU when we snagged it, but something must have changed quickly, because by late August/early September the required TPUs for most 2014 weeks shot up to around 42 TPUs, and I saw very little popping up on the open exchange inventory after that.
If you're looking for a trip next July, you would probably be getting a match sometime around the beginning of 2016, but you should get your ongoing search set up as soon as possible. The earlier you get your search set up, the higher you will be on the list when those dates and properties get released into RCI. Getting the search set up early is especially important if you want something other than SSR or OKW. Also, if you're only looking for DVC properties, during the search set-up process don't select a region or sub-region for your search, just enter the DVC resort codes for the resorts you're interested in. I first had our search set up with the region and sub-region AND the DVC resort codes, and apparently the RCI system basically just ignores the codes and kept putting holds on the same grimy-looking Orlando-area unit that matched our dates. Once I removed the regions we stopped getting random Orlando-area matches and just waited until we got our DVC match.
As other posters have pointed out, only going for BLT is going to make it very tough to get a reservation. When we went, we had backup, non-RCI plans if the exchange didn't pan out, so I only ran the ongoing search for the EPCOT and Magic Kingdom area resorts. But the inventory in RCI has changed a lot in the last 2 years, so I doubt we would luck out like that again. Honestly even after staying at Boardwalk, if we could get my in-laws to consistently deposit their weeks in RCI in advance and get a search set-up, I would be excited about trading into any of the DVC resorts. It is almost impossible to beat that price for an entire week in a 1 bedroom DVC villa, and each resort has its own positives and negatives, even BLT. Once you get matched and you know where you'll be staying, there are owners/fans/lovers threads for pretty much every DVC resort, so you can look at all the pictures and adoration on the thread for your resort to get pumped up for your trip. I used to think that AKL and SSR were both so isolated and thought I would never want to stay there, but after reading up on them and the amenities and experience that they each offer, they both sound like great places to spend a vacation. We're planning on renting DVC for our next trip and it's actually been really tough to narrow down our top choices!
Here is a mini-guide on RCI trading that I made for my sister-in-law last year, so it might help walk you through the process of setting up an ongoing search. I would also suggest asking your FIL if he will give you the login info for his RCI account so that you can get the search set up and monitor it on your own, instead of depending on someone else to do it. My in-laws have had a timeshare and an RCI account for years but have never understand the whole ongoing search vs. the leftovers that pop up in the open exchange inventory, and they especially did not understand the importance of getting a DVC search set up well in advance of the travel dates. So instead of having to listen to us explain how the exchange system in RCI works, they just gave us their login info and we were able to do it ourselves.
I hope it works out and you're able to trade in!