T.S.
S.,
Follow your instincts and what God has put in your heart. Sometimes we try to ignore that little voice inside as if it is our own thoughts, but really that is God answering you and it is not our own thoughts at all. Just keep praying about it and you will come upon the right decision.
I truly believe that God works through us in mysterious ways and we can make a difference in this world for others. There are many ways you can help the father of your child without sacrficing what your grandchildren need.
My thoughts and prayers are with you during this difficult time. Just keep God in your heart. He will always get you through.