You could attach a small drop of Elmer's glue to the bottom center of any of the ones you mentioned and cross the ribbon... long ones, on the glue and bring up the ribbons, tie and hang on tree, with the plates, etc. setting flat. Hope this helps a little.
Your tree sounds very sweet!

You could use plate hangers. Like they use to hang plates on a wall

I'm thinking about hanging some tiny plates on my tree and may just use hot glue to attach some sort of hanger. The hot glue can be removed with a heat gun later if I want. Have to decide soon, hope you get a brilliant idea from someone else that I can use too!

Also there are the glue on hangers you can get at the dollar store with a triangle hanger attached to a fabric piece that has glue on it. I used them years ago to hang things on the wall and they worked pretty good til I washed the plates, then the glue comes off.

I will second the hot glue idea.
I've used it to hang many items on a tree that didn't have
a 'hanger'..works very well.

A couple of years ago, I purchased a small tea cup & saucer ornament, as a gift. The two were hot glued together and hung that way...You might want to try that on a few, for a different look.

jane