I think that you're being a little bit conservative with all three. Assuming our results continue to be as good as they currently are.
If the Ipswich game goes ahead we should be looking at 9,000+ as an absolute minimum. They'll bring 1,800 and we would surely get 500 more home fans for them than for Rochdale? Similarly I think both Wycombe (really!!!) and Lincoln will pretty much sell out their allocations. As much as they're not our historical rivals in the way of Swindon or Reading, there is a bit of local rivalry with Wycombe, and I'd expect 7,500 to 8,000 home fans, maybe more, so we should be looking at 9,500+. Lincoln travel very well at the moment and I'll be both surprised, and very disappointed, if we don't have 8,500+ home fans on Boxing Day, so therefore 10,000+ total attendance.
These are the sort of games which will entice people to come back, a bit of feistiness, a big crowd, and a sense of occasion. As far as marketing these games is concerned these must be targeted not just at the existing, or lapsed fan base, but at the thousands of potential NEW fans that are out there just waiting to be excited by a day at the football. As I said previously the likes of Rochdale just do not have the appeal to the floating or non-committed supporter.