We have wonderful trips each time no matter where we stay! I don't think we miss out on any magic when offsite (just stayed at HOJO this week and had plenty of magic, even got dream lanyards and pins!) Our magic happens in the parks, not when we are sleeping.
That said, I do like to stay on property occassionally! And if I didn't go so often, I would most likely stay on property every time. I love the Grand Californian and I posted on your other post with some good rates for October.
When it's warm enough to swim, we stay at HOJO because that has the best off-site kids pool area hands down! We take a break when the hours are long, but depending when you go in Oct., the hours will most likely be 10-8 in which we usually don't waste park time to swim. Then again, I guess it would make a difference how many days you are there.
We also stay at the Desert Inn and Suites because of the great price and extra room/bathroom which helps with little ones!! It's clean and very close (as far as our DTD room was at the Grand) so it's easy for little ones too! But it's nothing fancy so not sure if that's what you want either.
Good luck, you will have a great trip either way!!
Andrea