You could just buy some gold fish at the store. They're super inexpensive... Then just put the bowls on the tables.
I should have said though... she is a huge animal person, and this is one thing she absolutly hates at events... especially if you are telling people to take them home... she feels that you are "making them care for something they may not want" and therefore they are not going *in most cases* to be taken care of properly. Although, I know they are just goldfish, but she (and really I) are kind of against it... (like I said, she is a huge animal person, and so am I, and working at petsmart at one point, you really see the people that come in hating that they got this fish and now have to take care of it, or the people that come in and don't care and just buy the fish knowing they don't have to worry about where they go after the event.)
Thanks for that idea though!