By not thanking you promptly, the family is letting you know that they are just not that keen on receiving these photo books every year.
They are also extremely inconsiderate to not tell you this directly.
As well as not properly thanking you.
OP,
I think what you are doing is very kind however the family may be feeling a little uncomfortable w/the time + money that you are spending each year.
And you really do not have to gift the parents anyway.
Especially the extended family.
You sound like a truly generous person overall.
