Of course, you can be nice about it! Why wouldn't you?
If the gunsels HAVE to go into your horse's paddock, then you need to teach them exactly what to do when baby comes up to play. Get that clear in your mind, & then give them easy, specific directions.
For example, you might want them to carry & twirl a rope at her every time she approaches them, but calmly, without undue predatoriness!
She doesn't need to bond with them, but only with you, so that might be a viable solution.