What is a friendlier way to write "at the * preference" and "at the * convenience"?

Solution 1:

A common error (faux-pas) made in incoming phone messages is the receiver saying "I will return your call at my convenience." That's a non-welcoming use of the convenience phrase. It is polite to ask one to do something at "Their convenience" not your own. Otherwise you are saying "I'll do it when I'm good and ready." Here saying "At your preference" or "At your convenience" is polite enough.

The context I would assume here is to describe what a hypothetical family or citizen may choose to do. Consider whether it is a family or an individual, a friendly word for citizen, being described. Then whether they may want to do it or not is their preference. Whether they might be able to do it or not is their convenience. Any combination of these would certainly be understood.