I agree with Lisa K. When my father-in-law was diagnosed with brain and liver cancer a few years back, the family wanted to put our lives on hold. My father-in-law flipped and demanded that we all live our lives to the fullest. This would allow him to go a very happy man. His wonderful attitude made the trauma of the situation easier for us. He passed away 2 months after he was diagnosed but was the happiest I ever remember seeing him.
No one can advise you on what is the right or wrong thing to do but allowing your father-in-law to have input in your decision will let him know how much he means to you. I would also let your daughter be there when you talk to him. I think this will also help heal your grief if something should happen while you're gone, if you do decide to go.
My prayers are with you and your family during this time.