Hi Tim
Not easy is it, when you need your Disney Fix but have kids in school!
As you mentioned Xmas as a possibility, I thought I would post just to say that prices drop on Christmas Day for Virgin packages, I don't know if this applies to flights booked independently though.
We are driving down to Gatwick on Xmas Day (hoping for clear roads while everyone else is eating their Christmas Dinner!) and then flying out to WDW on Boxing Day for 15 nights. It does mean that the children will miss one week of school but we felt that 5 days missed isn't too bad.
If you go before Xmas Day prices are much higher, I'm sure we will still get that Xmas Disney Feelin' turning up on Boxing Day! From what I've read on the Boards, the decorations stay up into the first week of Jan. Another bonus is that as you get into early January, the crowds thin out so we will have some time towards the end of the holiday with shorter queues for the rides.
We got a room half price at the Dolphin with our Disney Club card so it is possible to get a good deal for this time of year. There are actually codes out at the moment which apply up to Xmas Day for Disney Resorts, so if you started your trip on Xmas Day you could get a good deal, you can check out rates folk have got on the codes on
www.mousesavers.com
I don't know whether you were thinking of this year or next, I don't think there would be much flight availability for this year now, and prices would have probably leapt up, but it might be worth checking.
Hope this helps, or maybe you know all this already!
Let us know what you finally decide!