What Delmar said...
Just make sure you do your research on that forum. Dis has set up some very good rules to follow. Once you get an idea of how it goes, make a post with how many points you need and how much you're willing to pay per point. Then people will post back with what they have to offer.
If you use the link I provided above, you can check out the point rates for each resort for the year. Now if your trip over-laps a "season", your points will be based on your check in day.
Once you find some one to rent points from, your communications will be through them, not through disney. You can add the dining plan for something like 40$ a day per adult, 20$ per child (3-9), or you can go with the quick service dining plan for a lesser price. But since you'll have three little ones eating off your plate, I'm sure you'll want to do more buffets than al a carte (that is if the two youngest are eating solids), so the regular plan might be better. And that means you can add in more character meals, which would probably suit the children more than waiting in line. In some cases, they're a bit over rated. But without having to wait in line with 6 kids, I think it'll be worth it for you.
And yes, this way you can use your GAD tickets for upgrades, without having to buy a seperate ticket. Just use the tickets the first day, then visit guest relations on your way out.
Disney understands that most DVC owners probably have annual passes and therefor buying tickets for their vacation is not necessary. So they're eligable to add the dining plan to their room reservations.
We can make this work for ya. You just have to ask.