A couple of suggestions for whack a ghostring:
1) To encourage participation, I think players should still get 1 ticket as long as they get at least 10 points, similar to what was done for shadow tag.
2) To avoid stalemates & situations where there is no winner even with 2+ active players playing extremely well, I think that the bad ghostrings need to despawn after a certain amount of time. Even if it's like 20-30 seconds. Just as an example with 2 players: assume neither player hits any bad ghostrings. If they are roughly evenly matched then usually neither player will achieve the 35 points necessary to select a winner. The game quickly gets to a point where all remaining ghostrings are bad, and neither player will click on them.