First off - DON'T PANIC!
I'm guessing that this is pretty much your first experience at performing for total strangers, in an 'employed' (albeit unpaid) capacity?
You're now on the confidence curve that all newer performers (especially in a close-up situation) have to deal with; it's not only that you're performing for an unknown audience, but that you are doing so in an environment where such a performance is pretty-much entirely
unexpected.
When dealing with a table comprised of only adults, you MUST both expect to experience, and
plan for, being knocked back.
Basically, prepare an 'out' line or two, to retreat from uninterested tables politely, and leaving the fools with a smile on their face.
Move then, STRAIGHT AWAY, to a table distant from the last one approached, and try again...and keep going, until you get a 'taker'. At this point, play one of your sets, and try to ensure it's one which provokes an audible reaction (either laughs or screams!) towards the end.
By this time, you have all the tables in ear-shot paying you some degree of attention, and you'll find it VERY much easier to get a positive hop to the next, as a direct result.
If all else fails, try an easy-opener with a likely client, and get them to see some magic BEFORE they even know who/what you are.
One, that I used to use some years back, was to approach the table with a disposable lighter in my hand (not a clipper type - one of the 'lozenge-profile' types), with printing/a logo on only one side.
I'd approach the 'table head' (usually the father/boyfriend/husband), and display the printed side of the lighter, saying that I'd found it by the table, and asking if it was his?
On receiving a negative, I'd comment on how I should have realised that was the case, with it obviously being such a cheap bit of tat. At this point, I'd rub the lighter, and perform the pad**e move, showing that the printing had rubbed off/then come back/was then on both sides/was then on neither side....
At this point, I'd admit my guilt...own up to being the resident magician, and would ask them if they'd like to see a little more.....
...Most, even if they'd have been initially disinterested in magic, would now be gagging for more of the same.
/Trade Secret mode Off
The most important point, though;
NEVER, EVER give up on a refusal, like you did on this occasion. I know how difficult rejections are, believe me....but you
MUST keep going, keep pitching and ONLY end on a high.
Please let us know how you get on? This is exactly the sort of 'hands on experience thread' thread that is SO useful to everyone here.
Hope this waffle's helped!
Rob