Originally Posted by PaintHorseMares
Putting a weanling in with adult horses is rarely a problem. The adults don't see a weanling as a threat to them and generally just leave them be.
And it is a very good thing to have a baby sitter for a young horse. I would never leave a young horse by themselves. I would make a POINT to find a buddy. Sounds like a good set up.
And yes, it is good to introduce them before sticking them in together!