Business etiquette question - What would you do?

I run my own, small CPA practice. I recently invited someone to lunch, so that he and I can get to know each other and discuss some networking/referral opportunities.

The man’s very excited about our meeting…so much that he wants to have one of his colleagues join us. He went ahead and invited this other guy.

I have no problem with Man #2 coming to lunch. In fact, I’m glad he’ll be there. The more contacts I make, the better for me.

But, I offered to treat one person to lunch, not two people. I think it’ll be bad form if Man #1 expects me to pick up the tab for someone he invited.

Not only is the etiquette question on my mind, but I have a monetary concern. My business really is quite small and has modest revenues, so I can’t afford to wine-and-dine many people.

When the check arrives, I might say, “David, I’m so happy that you could join me today, and of course I’m covering myself and you as my guest. The portion for Michael’s lunch is $____.” Is that too tacky? What would you do?