Do I have to have my Covid shot card with me or a picture of my card on my phone will suffice?

I would take card and they check ur I'd and u have to wear mask the whole time.

I used the picture on my phone in Google Stack

You can have a picture but you need to have matching ID. My son is 12 and they will just ask them to confirm their birthday

A picture is fine. That was all they required at the Christmas concert last month.