As far as Carson's red goes I think the club can clearly argue that nobody could say with certainty that the ball was not in the box. Like with corners surely the ball does not necessarily have to touch the paintwork but 'break the line' above it. Also, keepers no longer get automatic red cards for handling outside the box but only if they are preventing a clear goalscoring opportunity. This was by no means a clear opportunity.
For Dunne's red we are back to the 'accidental' argument, if he even touched him at all. Under the new interpretation of the rules this could have been dealt with by a yellow card in my opinion. I think the club would be entitled to challenge both cards.
As for McHugh, that was just foolish.