If it may help in some small measure:
NM had no formal system of recording deaths until 1919;I tried every known database for them to no avail;the best you can hope for there is a county record, if McKinley county kept such records.
You already know that Opal was with aunt and uncle Matt and Clara Mattson and family in that county in 1920;and John and Delbert were next door with Charles and Myrtle Barker and their sons.
In 1900,Clara and Nora Barker lived with their grandparents John and Elizabeth Barker and uncle Charles in Kansas.
In 1910,the Mattsons and Davenports lived next door to each other in McKinley county:
Davenport,James-35,married 4 years;born TX,parents born IL;farmer
wife-Nora-19;born KS,one child born,one living
and Charles Barker age 25.
If it might help connect dots: Matt Mattson is shown to be divorced in 1930,three children and a daughter in law with him. He died in 1931;Matt Jr. died in 1956 and son Charlie died in 1937;they and Charles Barker are buried in Hillcrest cemetery in Gallup.