From Debrett's 2008:
Grandchildren of Sir Robert Gunning, 8th Baronet & Ann, Lady Gunning:
1. Sir Charles, 9th Bt (1935 - 2020) - 1 dau
2. Iseult [f] (b 1936) - 1 dau & 1 adopted son
3. Marion (1937 - 1939) - no issue
4. Elaine (1939 - 2019) - 5 sons, 1 dau
5. Sir John, 10th Bt (b 1944) - 2 sons, 1 dau
6. Joseph (b 1946) - 3 dau
7. David (b 1948) - 2 dau
8. Henry (1949 - 2020) - 1 son, 4 dau by 2 marriages
9. Bernard (b 1951) - married but no issue
10. (George) Peter (b 1953) - 1 son, 1 dau
11. (Anthony Andrew) Simon (b 1955) - 1 son & 1 adopted son.
This makes a total of 26 grandchildren (incl the adopted grandsons) - so we are 2 short. We know from the obits of Sir Charles, Elaine, and Henry that we have a complete set of their children. Searching around suggests that Simon's son Dylan (b 1986) has children, probably a boy b 2014/5, but the date of Simon's marriage is given as 1986 with no months, so it is difficult to be sure if Dylan is in remainder himself.
There seems to be good evidence for a further son of Simon: Matthew John Wilson (of KY/FL) who m. Crystal MACHON and has at least a son and a dau. Difficult to be sure if Matthew is in remainder as Simon already has one adopted son.