The Queen Mother was still attending luncheons and receptions as well as receiving a variety of people.
The Queen will still be expected to read her boxes, meet weekly with the PM (there are c 50 of my 150 engagements by the way), attend 12 council meetings a year - up to 62, attend Garter, Trooping, Thistle and Ascot (another 5 - allowing her to only go to Ascot 2 times rather than 5 now) and Epsom plus receiving in audience - meet, shake hands with and small talk for about 10 minutes at a time - 50 ambassadors/high commissioners and we are at 120 or so quite easily.
This is NOT having her go outside BP for the most part but have the people come to her and if she can't do that then she will have to abdicate as only she can do this stuff and it is really the important part of her job.
Attending Garden Parties in BP or Receptions and Luncheons is also possible - and could easily add another 20 - 30 with again not actually leaving home.