Thanks for that tip, Bean.
currieg, I assume you're staying in Cavan the whole time?
Co. Cavan is quite pleasant, lots of lakes and hills. There are lots of little country roads leading to Lough Oughter between Cavan and Killashandra, so this might be nice for a leisurely drive and some walking.
One day you could go to the Cooley peninsula which is north of Dundalk in Co. Louth (Cavan - Dundalk is about 51 miles). This would not be too far. The peninsula is a gem and Carlingford is a small medieval town and certainly worth a visit.
The road from Cavan to Dublin (N3) leads you through pleasant countryside, a good stop is the Park Hotel in Virginia. Depending what time you're leaving Cavan on the Sunday morning you could even take in the Hill of Tara south of Navan.
Please don't forget that ALL pubs will be closed on Good Friday. Some hotels will be open, though, if you're looking for lunch or dinner.
Have a lovely time at the wedding and I hope you'll enjoy Cavan.