I think you should advise him of your health situation and discuss the situation w/the children. You can ask him if he can go w/you for the testing and surgery, but I would suggest that you have a back up plan in place just in case he can't assist you or your children. Now is not the time to be shy about asking a close friend or neighbor to be of some assistance to you.

I hope that everything turns out okay for you. I will keep you in my thoughts and prayers.

Sit quietly, the answers will reveal themselves when you least expect them to.
The past is gone, the present is a gift and you need to focus on today, allow the future to reveal itself when it is ready.