The "Gardens" consists of a main house, and a set of cottages in the area. There is access to the sea, but it's a long walk on a slippery path and the sea in Ireland is pretty rough, very cold and can be dangerous. Unless you're extremely confident in your swimming abilities and hypothermia is not an issue, go the local swimming pool in the nearby village.
We spent a week there in August 2012. It did rain a lot, however we did not allow rain to spoil our time there. We had a good time and good company. We were staying in one of the houses in the estate. 2 families each with 3 children. We made a good use of the fireplace.
The place is convenient if you have kids 'cause they can go around the garden w/o too much supervision. Of course they need to be careful 'cause there are farm animals (from dogs to goose and horses), but the kids loved the place. Once we equipped them with Wellingtons everything worked fine and the mud stayed out of the house (mostly).
Valentia Island is a nice location, basically "on" the "ring of Kerry" and you can take day-trips to several locations.
The only negative note was that we had several problem with the house appliances (stove, oven etc.) which were old and a leakage in one of the bathroom that requested the intervention of a plumber.
A note of caution goes with the fact that if you stay at one of the cottage like we did, you've to plan in advance what you gonna need, 'cause the nearest store is off the island. There is actually a very small one by the port/ferry, however they only have very basic stuff.
All other things equal, it's a place I would recommend especially to families (also large one) who wants to spend time together in a nice place w/o too many frills.
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