The primary purpose of her being children's programme coordinator is, of course, that it allows Lynn to nag her family about not being supportive enough of her career without alienating her readers. They might not be able to really relate to Elly being baffled by legalese and finance-speak or having Not-Cathy Guisewite congratulate her on avoiding the mistake of giving her fictional family her real family's name, they can relate to children and husbands who are too invested in Life As It Was to be happy for them. For the next ten or twelve years, we can expect strips that depict Elly's families as jerks who want her to be chained to the stove.
Why, we even get a sequence about how thrilled Elly/Lynn is to leave the stifling environment in which she usually finds herself. She has a grand old time at the convention. So grand, in fact, that she doesn't notice that part of the stifling environment comes with her when two straw Neanderthals bitch about how letting women out of the kitchen causes chaos.
This leads us to the other important means by which Elly being the lady that runs story time allows Lynn to slam people she hates over the head. I remember in one of her retcons how she growled about the insane priorities of the government:
Why do so few businesses and organizations support the arts? (Don't even ask the town council. There's a sewer to fix and the arena needs painting.)
and being reminded of her drive to keep the city from 'wasting' her tax money improving said arena and invest it in saving the historic (and not 'decrepit', Michael) town hall. Simply put, Lynn also loves to use the library as a means of complaining about how the taxpayer should stop supporting roadwork that makes commuting such a trial and sports venues where men learn to beat up women, children and gay people and support the arts. Nowhere in her point of view is there any room for the idea that they don't make it worth anyone's while to do so.
This leads us to the final purpose of the library: to complain about how the job market seems to have no room for the Elly Pattersons of the world. Had not the miracle happened, Elly would never have found a place to pretend to be an employer. The odd thing is that after she got cut and replaced by a high school student, we never saw the inside of the place again. It's like how a lot of characters simply vanished when she was done with them. My guess is that the Nichols children, Darryl Smythe and Janice Madigan all hang out there wondering why they've been given the Chuck Cunningham treatment.