What happens if Always Watching is destroyed mid-combat?
The ongoing effects from Always Watching end as soon as it is destroyed, so your creatures no longer have vigilance and +1/+1 by the time combat damage is dealt, and both Gliders will die.
However, your Kitesail will remain untapped because vigilance is only important at the moment attackers are declared:

702.20a Vigilance is a static ability that modifies the rules for the declare attackers step.
702.20b Attacking doesn’t cause creatures with vigilance to tap.

So your Kitesail remained untapped when it attacked because it had vigilance at that time, and the game does not rewind and tap it just because it lost vigilance later.