Found: YA books fantasy

Need help finding a series of books about some kids that when they stepped on stepping stones they went through a portal to another world where there were unicorns.
That is all he can remember about them, re read them back mid 80’s
Thank you so much

The Time Keeper by Barbara Bartholomew?

Possibly something from Bruce Coville's The Unicorn Chronicles?

>2 MissSquish: Thank you this is the one! Much appreciated

Great series. I've read all three. Looks like a couple are finally on openlibrary.org to borrow.

>5 bookel: Thank you will go check them out!