Yes, 100 years after the 1911 census, Mount Sackville Convent is still a community of the Sisters of St Joseph of Cluny. Its address is Chapelizod, Dublin 20, just on the edge of Phoenix Park.

The Guinness house at Farmleigh was bought by the Irish Government in 1999. You can go on a virtual tour here:
https:// www.
farmleigh.ie/VisitorInformation/

P.S. it might be instructive to look up the household schedules for George's neighbours in 1911: were they all perhaps employees of the Guinness family, living in tied cottages or similar? I have only looked up two so far, but both could have been estate workers (Andrew Morton, land steward; and Charles Nichols, gardener).