Yes!
The holly should last ok as long as you dont have your wreath indoors
The eucalyptus will start to dry out but if you use 'baby blue' it will still look good anyway.
The tree ivy is the one that may not last till xmas. we tried this one year as added decoration but after couple of weeks it looked a bit sad.
Having said that, if it's for yourself it's not a problem 'doctoring' it if it becomes necessary.
As you are doing this for the experience, i would use it all anyway, you will then be able to see for yourself how long these materials last. If you are able, make 2 and keep one out in the rain/weather and another one undercover and see the difference in a few weeks.
As to conditioning, yes, give them all a good drink, especially the ivy.
Good luck.