pregnancy announcement ideas

Mini
My SO and I are going to lunch with his dad for Father's Day, and he told me that he thinks his dad would prefer for me to let him know that we are expecting (as opposed to my SO telling him) and we decided we would tell his dad at lunch. Does this make sense?? Lol sorry if it doesn't.. anyway I've never met his dad before so I feel like it's awkward and idk how to tell him! I don't want to just straight up say "I'm pregnant" I want to do something cute where he would be confused at first and then he like OMG! (Like when gifting a onesie to announce). Any ideas?? Hallppppp