I don't think I'd do anything with them until at least fall 2019, Karen. You might have quite a few more come up next spring! The roots will still be smaller around than a pencil and probably less than 6" long after another year. I left my Molly seedlings that first emerged spring 2015 in place until last fall, they are all up and doing well! Also have tree peony seedlings that emerged spring 2015 that are actually going to have a woody stem this year, whoo hoo!!! Still quite a while away from a bloom, though. Still have a couple of tp seedlings that I didn't transplant, only 1 each in a 2 gallon pot buried in the garden, as well as a couple of Lemon Chiffon seedlings from the 2014 APS convention. Also have some species and Rockii crosses from 2016 convention that came up last spring, still in the pots in the ground.
One thing that I found out the hard way is that you need to keep watering those seedlings through the summer if it gets dry, Karen. I lost several Phoenix White seedlings because the ground dried out too much--the established peonies were fine but the seedlings shriveled and died away.