If you can get a tree direct from the grower and get them to cut it down specially for you, rather than having one ready cut. Then what I usually do is choose a coolish place in the house, saw a builders type blue barrel in half, and cover with silver foil. Put in the tree and wedge round with blocks / bricks for weight, and cut off the lower branches so it is sitting on the barrel rim..Tie the tree back to a hook you have fixed in say a door frame for extra "no falling over security" use ties in two directions if necessary. Top up the barrel with water and plenty of "flower food"
I keep a pump up sprayer/mister handy, and spray it with moisture whenever I can, and make sure the barrel dosen't run out of water. I usually have a Nordman Fir as it is nice a thick, and I used to put it up just before 1st Dec, and it did last til 12th night but only just.
For wreaths I use those "florapack"type bases and again keep them watered and sprayed. Ivy in berry (lots in the hedgerows) with some variagated ivy and cones etc looks good, and some really nice wide, wired ribbon, in red, or maybe tartan would be good for you.
Have a lovely happy time - Congratulations
All the best
Sue
Dark Brown Eggs