The Mom to be did not smile in any photos, their kid was not cooperating, and her husband did not want to do them.
Please, do not take my writing as offence, but explaining.
This is where difference between experienced photog and "40$" is. It is not just because of the gear knowledge and not because the minimum charge of pro photog would be if not 400$, but 200$ at least.
First, if they knew they have to pay $200, not 40$ their attitude towards you would be different at get-go. For $40 they feel free to trash it.
Second, now you know what taking pictures of people profession has not only gear part involved. Pro photog would make her smile, kid cooperating and him willing to participate. Well, if photog is on assignment by agency and photos must be taken.
But in your case telling customer what they are not ready is part of profession as well. It is two sides contract. You come, you are ready. If they are not, it has to be explained to them. Here is no difference between plumbing and photography. If plumber is called to come, but no access is provided - kiss my ars and goodbye. Same is with photography. Scheduling session and not willing to participate is their fault, not yours. You could have it in written before you could start, BTW.