I think the £17 day return go anywhere fares will have finished on their Club50 - but check.
I hope that the smart card that Club50 is loaded on arrives before you leave. You can't get them reissued at ticket offices I believe.
I already have my Club50 card, and for the 4th I have a return trip from Inverness all ready for collection in printed ticket form from a
TVM▸ near me. 5th remains up in the air. If the Highland had only built its branch to Kinlochbervie, I would renew my acquaintance of over 50 years ago with that community.