It's a pleasure!
Frederick & Mary Elizabeth were the children of John & Mirose. I've found the family in 1871 in Newcastle, where Frederick's full name is given as Frederick Sparkes Greaves (born in Penkhull), his sister Elizabeth was born in Newcastle & there's another child too: John Jarvis Greaves age 6 born in Newcastle. Myra/Mirose's niece, Elizabeth Timmis age 21, was also staying with the family (she was the daughter of Mirose's sister, Elizabeth).
Of the other grave inscriptions from Fradswell churchyard that Alf has collected, Elizabeth & James (as you have deduced) were Mirose's parents, Edmund John being their youngest child. And James & Sarah Capewell were her grandparents. There were a lot of Capewells in the Fradswell/Milwich area in the 19th Century - it can all get rather confusing!