I wanna breed my miniture pony would this work?

There doesn't appear to be anything wrong with them. I don't see any reason why you should breed as long as your prepared for the foal and of course all the expenses. I do recommend that you get them checked out by your vet. Animals with dwarf legs are at more of a risk for heart problems. If you get a clean bill of health for both horses then I say go ahead. Good luck!