In theory - but not in practise.
There is only one flight from Knock to Edinburgh a day, and it's at 5:10pm on a Saturday. So they'd need to fly over the day before and stay overnight.
The problem with coming back is that there is only one flight from Scotland to Knock as well - and it leaves on Saturday morning. So to get back from a Peterhead fixture via Knock, they'd have to fly on the Sunday and spend a second night in accommodation.
So it's not just the journey time involved in getting from Sligo to Knock and from Edinburgh to Peterhead, it's the fact that it needs to be a 48hr trip with 2 night accommodation thrown in. That would be a big expense for Sligo, so they've dodged a serious bullet in this round