Well, check out the logistics:
ID = 52 possible revelations
Dartboard: 20 'easy' targets, plus the bullseye. (21 selections possible)
Personally, I'd tuck the cards behind the wire numbers (I've done this before) in a fan around the board, one card per number.
But to add credibility, give the mini deck to a spectator. Ask them to shuffle and check there are genuinely 52 cards.
Also hand them a jiffy bag (ID inside) marked PREDICTION, and get them to keep a hold of it. (Actually, a Brainwave may be a better idea for the visual)
Now, ask the speccy to select 21 cards totally at random, leaving one face-down and placing the other 20 face-up behind each wire number.
The face down card is the 'bonus' bullseye card. This is sneaky... in the caffuffle, I'd personally switch this card for a 'known' card, and put a large duplicate of this somewhere as an extra special revelation should anyone hit the bullseye.
Anyway, back to the plot...
Choose a speccy to then throw three darts. At ANYwhere on the dartboard—not necessarily aiming.
Now, ask another speccy to remove 2 darts.
There will be a final prediction. Ask for all the remaining cards to be removed.
At fingertips, take the jiffy bag, and do the reveal whilst standing with the dartboard and the final selection visible over your shoulder.
Re-cap slightly as to exactly how random this was (i.e. the choices of 3 spectators!).
Reveal the 'turned over' card from the deck.
I've performed this effect with regular sized cards, but I like the unusual aspect of the mini's
