Why would I want to add on points? Because you'll get addicted to the good life (like the rest of us). We thought, "well we've been happy staying at a value, so, the studio is plenty of space". But, then, we spent 3 days in a 1 bdrm and LOVED it. No, I wouldn't want to HAVE to cook on vacation, but, my food allergies make many of the quick service places a challenge. So, having a kitchen to make simple meals in was FABULOUS. Plus, the ability to put my laundry in before heading out to a park and the switch it to the dryer before bed and have clean clothing the next day without having to babysit it, is also fantastic. (Yes, I used to just bring extra clothing, but, really I prefer carrying less.) So, now we mix and match and sometimes stay in studios and sometimes in 1Bdrms. If we had more points, we could always stay in 1 bdrms.
Why would I want them at a different resort? You can book at your home resort at 11 months and at other resorts at 7 months. So, if there is a resort you KNOW you must stay at for certain occasions, then you'll want to own points there. We've never really had trouble getting resorts other than our home resort, but, there are some high demand categories (such as OKW 3bdrms, BWV standard and boardwalk views, etc.) where I wouldn't count on it.
If I buy Bay Lake can I still get the Grand Villa at Old Key west? And would it be difficult to do so? Technically, you can. But, the chances of getting it aren't likely.
Last question ... the world passport collection, is that seriously only 124 points a week? or is that per person? (My points may be off I have an old book) I think that at a FEW resorts in their smallest rooms you are correct. However, the world passport collection is fairly non-standardized so I wouldn't count on this. My calculations (which I did with 3-4 different properties) were that if I wanted to go to most of these places I'd come out ahead by renting my points and then booking them for cash. But, the point rental market hasn't been keeping pace with hotel rate inflation so this may not still be true. I certainly wouldn't recommend buying into DVC if your primary intention is to trade out. However, you will be able to go lots of other places using your DVC points if you choose to do so.
SO what is the deal with the food plan? The food plans are the same as the ones available to guests who've booked through CRO. But, in order to book the
DDP or the DxDP as a package through CRO you must purchase at least a 1-day park ticket and there's a minimum number of nights that you must be staying. As a DVC member staying on DVC points at a DVC resort you can book the DDP or DxDP for any length of stay (although you must purchase it for every night of your reservation) and you do not need to purchase a park ticket. You can also add it to the reservation on relatively short notice (but it must be before check-in).
Is 250 enough? Maybe. I'd take a look at your wdw travel patterns in the last few years and your expected plans for the next couple of years and try to work it out. Some people work it out precisely for XX nights at resort YYY. Some people like to have a round number somewhere near their calculations. If you do decide to round, I'd round up since most people end up finding new ways to use points.
Do we have to use them or can we send family on vacation? You can send anyone you want on vacation. If you start sending lots of people with different surnames on vacation every year they'll check into whether you might be trying to rent commercially. But, if they are friends and family members (and possibly the odd renter) then you are welcome to use your points for their vacations.