I don't really see the catering side of the zoo too much as 9 times out of 10 I have my own packed lunch [I'm a fussy eater, and I can eat what I want whilst walking around] - If I know it'll be a quiet day and I'll have time, then sometimes I will buy food in the cafe.
The biggest problem is the time at exhibits, but members are just as guilty of 'hogging' exhibit viewing space as general visitors are [whereas I've seen members watching something for much longer, after all general vistors have paid a fair amount to get in if a typical family, so they'll want to keep moving and see as much as possible. We just need to learn to have a touch of patience
From my experience, a family will walk away from the exhibit after a few minutes. Of course there are the odd exceptions, but whilst crowds move painfully slowly in narrower parts they DO move.