If you do not get the help you need with your depression, and the children are not cared for because of it, I can imagine you could run into trouble.
However, if you are receiving proper help for your depression, and you have arranged for proper care for the children, I don't see that you could be seen by anyone to be doing anything wrong.
I assume your mother could care for the children IF you were hospitalized?
Generally, people don't get hospitalised all that much or long these days anyway.
By remaining untreated you and your kids are losing bits of each other every day...imagine how much more your relationshipsa could be if you were feeling better and had more energy and delight to share with your children!
It's great that they have a good relationship with your mother, too.
Go get help already. Don't let the drop kick dad make you feel too threatened to do the right thing by yourself and the children.
And I hope you are feeling better soon.