How can I cheer my dad up?

My dad was dating this girl for about 4 years and today my brother told me they got in a fight and broke up last weekend. She was a nice lady, but I could see myself getting annoyed with her a lot as well she was a bit loud and sometimes acted like such a teenager and she;s like 45. I didn't see much of her only like 3 times a year. Well anywho my brother said my dad was pretty upset when he talked to him. I am going to visit him at the station (he's a fireman) on fathers day since he has to work then I will stay at his house for a week this summer, how can I help to cheer him up, I will probably be seeing a lot more of him since he won't be with her as much now.