The best way to avoid stress is to plan well in my opinion! I'd suggest that you take your calendar or create one from the day you need it (until Christmas) marking off what needs to be done each day.
This way you'll get your shopping done early, your home will be organized, and you'll have everything in place fast simply because you've broken down the big tasks into little tasks that can be accomplished each day.
I'd suggest that you list out all the things that you need to do - Assign priorities to them and then break them down into daily tasks that can be managed easily per day. You have a plan to follow every day that will leave you feeling in control = no stress.
Hope that helps!