Hi,
Looking again at the 1900 census I'm not sure the the DOB for Inez is 1891 or 1897

I'm wondering if John has been enumerated twice on the 1910 census

(I have seen this before when someone is shown at home and also visiting relatives) or if only the first one is the correct John MCCONNOCHIE

1910
Census Place: Del Mar, San Diego, California
Roll: T624_95
Page: 7A
Enumeration District: 130
Image: 591.
MCCONNOCHIE John S
Head
42
Married for 17 years
POB: Eng English
POB of father of this person: Scotch English
POB of mother of this person: Aus Germany
Year of immigration: 1891
Speaks English
Trade or Profession: Civil Engineer
General Nature of industry: Construction R.R.
1910
Census Place: Santa Monica Ward 6, Los Angeles, California;
Roll: T624_87
Page: 11B
Enumeration District: 344
Image: 318.
MCCONNOCHIE John S
Head
40
Married 15 years
POB: England
POB of father of this person: Eng English
POB of mother of this person: Eng English
Year of immigration: 1891
Occupation: Civil Engineer
Eva
Wife
39
Married 15 years
2 children, 2 children living
POB: Scotland
POB of father of this person: Eng English
POB of mother of this person: Engl English
Year of immigration: 1891
Inez
Daughter
12
POB: California
POB of father of this person: Eng English
POB of mother of this person: Scot English
James
Son
9
POB: California
POB of father of this person: Eng English
POB of mother of this person: Scot English
Some of the POBs differ from the 1900 census but I still think it's the same family.
Regards
Daisy