Well, I went googling and found that there were no Christmas trees to decorate in colonial America. Decorations/ornaments did not appear until the Victorian era in the nineteenth century.
There were sites that listed "decorations" - holly, pine, most evergreens, and pomanders made with oranges/apples and cloves. That was about it.
http://www.history.org/Almanack/life/xmas/customs.cfm
Here are some fairly easy Victorian Ornaments:
http://www.victoriana.com/christmas/craft5-2000.htm
The other thing you might consider - paper. Stars, hearts, snowflakes, etc. were often cut from paper or cut into garland and used to decorate with. One of my favorite snowflake sites is this one:
http://www.daves-snowflakes.com/
The snowflakes are beautiful. I've used them with students as young as third grade. The "three fold" are much easier to cut if you are using regular copy/printer paper. I bought the CD several years ago, and my class cut over 200 of them and hung them from the ceiling for our "Winter Wonderland" Reading night. It was really pretty!