It sets a very bad precedent to give time away.  Ladies, you go to these meet and greets to hopefully find clients, right? Do you want dead beat clients trying to find the lowest rates and then expecting you to go to lunch with them (etc) sans fee becuz they are being so generous buying you lunch? Lunch being your payment/treat? Men who have established the mind set that you are a woman who expects less?  those are men who never tip but short you a few bills.  Those are men who pay you the discount rate you gave them 6 months ago when you needed to pay the electric bill urgently.  

What you sell is your time.. as much as so many of these men want to think it is something else (which is really disrespectful way to think about you).  

A meet and greet might be a very good idea but you (whoever organizes) should charge the men a small fee to attend.  IMHO at MINIMUM $25 but I would think $50 is more reasonable.  (that isn't much at all to hang out with a room full of hot chicks who are guaranteed to be chummy)

It would be a way to weed out the looky Lou's wanting to attend for the wrong reasons.
Especially if, as one poster suggested, you include the chat group that cannot be named.. which is primarily a group of the worst bottom feeders EVER... scumbags, game players, and all around disrespectful and problem people.  

If the space doesn't charge for a separate group meeting room then maybe divide what is collected and distribute to the ladies who attend with some stipulation that the lady must stay and really mingle for at least an hour.  The fine points would need to be worked out but I doubt too difficult.

Here I get preachy:
I expect the men are thinking their part is to buy food and drink ONLY.    
Like I said... Really wrong attitude for a client to have.  
You sell time ladies and to ask for a teeny tiny contribution for your time and beautiful companionship so many can meet is really a tremendous favor to the men.   Don't let them twist it around and make you think your total worth is the purchase of a drink and a biscuit.  You are a professional.. your energy and kindness and ability to make a persons world sunny is valuable.
Skills as valuable as a doctor or lawyers.  and you never hear someone say to a doctor "hey if you really like what you do why do you charge money for it?"

Only something to think about.   Do not give your time away.