12/23 and 12/24 will be crowded but doable. 12/25-12/27 will be extremely crowded, with MK almost certainly closing on 12/25 and probably on other days, as well. Whoever told you they went on Xmas week and had no waits was either lying or was talking about the week before Xmas. (She probably was talking about the Xmas season at Disney, which usually starts in early December).
That being said, with a little planning that week can be a lot of fun.
First, make sure you and DH understand it will be very crowded and you won't be able to get to do everything.
Second, make a plan for which days to do which park. If onsite take advantage of EMH. If not onsite, stay away from EMH park.
Third, make a list of must do rides, a list of rides you can skip, and a list of rides you'd like to do but if you can't do it you won't regret missing it. Make sure you do your "must dos" and fit in your others as time and opportunity fits.
Fourth, make Priority Seatings for any sit down meals you want. If you don't you will have long waits for lunch and dinner, eating into valuable park time.
Fifth, Use FP, use FP, use FP!!! Make sure you maximize it's use by learning how to hold more than one FP at a time.
Sixth, enjoy the Xmas time festivites such as: Candlelight Processional, Osbourne Lights (if showing this year), Holidays Around the World at Epcot, and the various decorations.
Seventh, avoid MK on Xmas Day. With crowds large enough to close the park you will not get on many rides/attractions. It will be wall to wall people. Unless you want to be able to say you were at MK on Xmas Day I, personally, don't feel it's worth going to that day. I recommend Epcot. Because it is so large and spread out it tends to handle the crowds better than the other parks. Plus, many people don't feel it's as "kid friendly" so they stay away on Xmas. (However, Epcot still will be EXTREMELY crowded that day as well).
Eighth, have FUN!!! Remember you are on vacation, in Disney, and it is Xmas time. Enjoy yourself and don't sweat the small stuff you can't control--like the crowds.
Good luck and enjoy yourself.