Is it rude to cook dinner for yourself when unexpected guest are over?

This is a little debate me and my husband were having.. his dad showed up unannounced at 4pm. We had already planned to make steak and potatoes and a salad for dinner. I had 2 steaks defrosted in the fridge. As 8pm hits his dad was still here and at that point we were both really hungry. My husband says I should cook dinner but we only had enough food for me and my husband not his dad. I said that it feels rude to cook and not have any to offer to his dad. He said that we didn’t invite his dad over for dinner, his dad just showed up announced and at this point we were ready for him to leave but didn’t want to tell him to leave.

We ended up ordering a pizza that neither of us really wanted because I felt it was rude to cook without having any extra to offer his dad.

So what’s your opinion would it of been rude to cook and not offer his dad any or perfectly fine since we weren’t expecting him and didn’t invite him for dinner?