We went for Easter a couple of years ago and had a great time. We booked a nice central apartment, which we found online (I don't have details, I didn't book it).
For activities, we decided that before we went we wanted to do a wine tour and see Aconcagua.
Our first day we walked around central Mendoza and compared prices between the many independent tourist offices there. In a couple of hours we had booked a minibus tour up to puente del Inca (must see) and Aconcagua AND received all the info we needed to make our own wine tour:
Taking a bus from the centre until one of the main vineyard avenues. Hiring a bike right there where we got off and armed with a map, leisurely cycling to several vinyards and an artesenal spirit and chocolate house. Lunch by the Vines, liberal lashings if wine and such. All very cheap. Just the rolling ride back to the hire shop is a challenge after an afternoon's consumation.
Aconcagua was mighty, and puente del Inca very special (inc. Standard Andean woolly garment stalls) although if you don't like long car rides with limited leg space this may be uncomfortable for you. The tour we took went all the way to the Chilean border where we climbed out at around 3000m to find an awe inspiring view of Aconcagua.
We went out to a salsa club Saturday night and met a local guy who invited all 4 of us to his parents house the following day, Easter Sunday, to join them for an easter parilla. Very fortunate and lucky we were.
Other things we didn't get to do but I have heard are good are the caves outside the city with have natural hot bathing pools in them and some of the lake and river fishing there.
The Hyatt on the main square in Mendoza has a very nice restaurant open to the public where you can enjoy a great Meal by their pool and swim too.
The best Italian restaurant I have ever eaten in is in Mendoza too. Calle Peru I think but ask. Someone will know.
There's a special street littered with bars and restaurants. This is the weekend 'strip' where everyone descends to enjoy the progression of the night. Both Family and young orientated (don't recall the name, calle something artesenales?)