Rekindled love after 52 years

I am presently dating my college sweetheart. His wife left him 15 years ago. He says that there are no chances of them ever going back together. He still maintains the household, is in a rut and can't seem to see his way out. He is very unhappy,and wants to make a change in his lifestyle. We love each other very much and get together about 3 times a year. He has 5 children and 11 grandchildren. He is afraid for them to find out about us. I am a widow, madly in love with a man that I cannot fanthom a future with. What should i do? What are my chances of ever having a lasting relationship with this man.

Is it acceptable for you to have a secret relation with this man, as he does not want his children to know about you?