This is what I know about their children...
Joseph Cooke, b1920 - with parents on 1921 census. Don't know what happened to him.
Lilian Edith Cooke, b 18 Sep 1921, d 1970 - your gran.
William Cooke, b 2 Jun 1923, d 1979 - with parents on 1939 register.
Ernest Cooke, b 1925, d 1926.
Doris Cooke, b 1927, d 1928.
Henry Cooke, b 25 Oct 1928, d 1988 - with parents on 1939 register and on ERs at Newlyn Road.
Dennis Cooke, b 1930, d 2013.
Sydney Cooke, b & d 1935.
Margaret R Cooke, b 1937 - on ERs at Newlyn Road.
There are a number of marriages listed that could be for William but no way to tell which if any are his. As mentioned, Henry appears to marry an Alice J Cumming (she is listed on the ERs at Newlyn Road). There are a couple of possible marriages that could be for Margaret R but again no way to tell which if any are hers.
Which leaves just Dennis who appears to marry a Grace Lilian Lea. They are listed as living in Droitwich from 2002 and there are matching deaths for both in