Lovely seeing others' ideas...I like the out of town trip and the dog!
My gifts will be varying hugely, because of the big age gap between my kids. For my youngest, I am making a sandbox out of leftover wood, and I have an unused tarp for covering it, so the only cost involved will be the sand and a couple of sand toys.
My daughter has outgrown her bedroom's decor, and while this sounds like an expensive project, if you stick to plain colors and shop around at bargain stores, can really work out affordably, allowing me to add one or two more extravagant bits that she'll love. This is great for personalizing - pin-boards, beading containers, frames,etc.
My eldest has been nagging for a cellphone, and initially, all I could see was $ signs, but having shopped around, I've discovered Net10 prepaid (no contracts!!)...handset prices start at around $15, though to keep her gift in line with the others, I may go for something more "elaborate" and for $15/month, she can get 200 minutes. She will also be responsible for paying towards the monthly cost, and the plan can grow with her, allowing me to buy more minutes as she gets older and proves her responsibility.
All round, I'm quite excited for Christmas to arrive and will be keeping an eye out for other ideas here!