#1 Must pack- COMFORTABLE shoes, and not the brand new pair that look comfortable either. Take shoes that have been broken in and that you are used to wearing. You're gonna be doing a LOT of walking so comfortable shoes are a must. It seems like a fair number of Dis'ers like
Crocs (or similar shoes) as well.
#2 Must pack item- A comfortable bag that can be carried all day long. Again, lots of walking so don't pack a huge backpack that gets heavy before you even get on the bus. If the kids are big enough small bags for them might be a good idea too. Inside the bags we usually carry bottled water, a change of clothes (maybe) for the littlest, and stuff the kids can do while we are either waiting in line or waiting for parades (although admittedly we don't do much of either...).
#1 Must see- With kids, it's gotta be the SpectroMagic Parade. My own two DS love it and it has been a classic for years. It looks like Spectro (at Magic Kingdom) will be going on Oct 3,6,and 8 during your stay.
#2 Must see- Wishes OR Illuminations. Personally I like Wishes because it can be seen and enjoyed from so many places around MK. Illuminations is best enjoyed from just a few places around Epcot and then there is the exodus of people leaving...
#1 Must do- Soarin! At Epcot this might be the best ride Disney has ever come up with. Everybody seems to enjoy this one.
#2 Must do- Relax. Spend some time by the pool. Unless you son's are all teenagers they (and you) will enjoy a break in the middle of the day by the pool. If you're staying at Disney the pools can be really fun.
So those would be my "must" do's etc. Of course it never hurts to read up on the parks and det an idea of the layout of each park. Also try to get to the parks early. I've never been in October so I don't know how busy the parks are but I've been in late July/early August and we've been able to do all of the rides we wanted to before lunch usually IF we were at the park when the rope dropped and used our FastPasses right.
Good luck and ENJOY DISNEY!