I am sorry, I don't know of anything called Ahmadis. All the sects of Muslims are Mohammadis and Ahmadis because they believe in Prophet Muhammad (saw) whose second name was Ahmad.
If you are talking of followers of MGA, than we may call them either "followers of MGA" or "Mirzai" as Mirza was part of name of Mirza Ghulam Ahmed.
I don't know if it is allowed to eat with them. May be some scholar can share an authentic hadith.
no point in makin things difficult, i meant mirzais as evident from my original posting.