We need a place for one night that's nice but not too expensive and has parking. Any suggestions?
The Glen Guesthouse on Gardiner St. has free parking in their garage (it's a bit of a challenge getting into it, but it's free). Their website is: www.glenguesthouse.com. It's a walkable distance to O'Connell St and the Temple Bar area, behind the Custom House.
Jane,
I realize this may not be doable, but if it's at all possible I would avoid having a car in Dublin. It's not necessary at all for getting around and will just crimp your style while costing you money.
Dun Laoghaire has lots of good, inexpensive B&Bs and is a 15 minute train ride into Dublin. We stayed at Ophira House. Parking was available there.