Glad your making the trip to 'God's Country' - I'm originally from Fermanagh - so excuse my bias.
Your hotel is very close to Castle Coole (Early Georgian Stately Home) - set in nice parkland with tearooms and walks. House is pretty impessive. Sometimes during the summer they have outdoor events in the grounds.
From the Round 'O' park in Enniskillen you can get the MV Kestrel boat tour around Lough Erne that takes in Devinish Island with it's monastic round tower. Boat leaves at 10.30am, 12.15pm, 2.15pm and 4.15pm daily. Tickets are £9 each.
Would highly recommend you visit the Marble Arch show caves - about 7/8 miles out of Enniskillen - but worth the drive. Ring ahead to check if they are open - during periods of heavy rain - they have to close.
www.marblearchcaves.net
When you are in the town centre - check out the Buttermarket if you want to buy any arts or crafts.
Your hotel is almost beside the Theatre. Not sure what is on but you can check at
www.ardhowentheatre.com
Pubs and nightlife will be fairly quiet mid week - but check out Pats and Blakes of the Hollow - neither bad for lunch.
For evening meal - would recommend Scoffs in Belmore Street - [broken link removed]
Then of course you have the shopping.
Hope you have a good time and come back for more.