В этом случае нужно запретить в UIGestureRecognizer одиночного тапа посылку события при двойном тапе. Делается просто методом - (void)requireGestureRecognizerToFail:(UIGestureRecognizer *)otherGestureRecognizer.
Пример:
UIGestureRecognizer *doubleTapGestureRecognizer = [[UIGestureRecognizer alloc]
initWithTarget:self action:@selector(handleDoubleTap:)];
doubleTapGestureRecognizer.numberOfTapsRequired = 2;
[self addGestureRecognizer:doubleTapGestureRecognizer];
UIGestureRecognizer *singleTapGestureRecognizer = [[UIGestureRecognizer alloc]
initWithTarget:self action:@selector(handleSingleTap:)];
singleTapGestureRecognizer.numberOfTapsRequired = 1;
[singleTapGestureRecognizer requireGestureRecognizerToFail:doubleTapGestureRecognizer];
[self addGestureRecognizer:singleTapGestureRecognizer];