I say no -> My family is unhappy -> BAD
Who will be unhappy? Your wife or your kids? It certainly is more status in being an elders wife... so I can see her point of view
But if you tell your kids that if you become an elder, they need to be good examples to all the other kids in the cong... I think that the kids might think that their father not being an elder, is a good thing...
And if you sit down and explain to your family that you rather spend that time with them, and really do that. (But then, of course, it is a "privilege"...). You can say that you need more time, and might say yes the next time.
And then, before next time, reduce you FS time to right below 10 hours, but just enough to avoid questions. Maybe you can allow your kids (depends on their age) to do something that an elder's child should not do (nothing really bad, but something that will make them/you a bad example).
I don't think this will make your family too unhappy, will it? And My father was an elder, and I sort of wish he wasn't.
Personally I think, as long as you just keep up your appearances for your family, you should not say yes.
kifoy