Hi Emma H,
I am from your area (Waterloo), and IMO your rates are too low. If you do wish to continue all organic (which I do admire, but with my experience with just how much food is wasted, would never offer for daycare) I would think you should charge at least 40, but up to as much as 45 a day. Most of the providers in my area charge $40 a day, and that is not offering organic. I just raised my rates last year, but with Bill 10, my rates are going up in the fall (along with some other contract changes)
About late payment, as long as I am paid on Friday it is due, I do not charge late fines. However it is up to them to get it to me, I will not stick around for someone to swing by and drop it off in the evening. I actually like to be paid by e-mail transfer (no trip to the bank needed!)IF they are late (and I did not agree that they could be) I charge $5 a day late fee, so monday morning they need to add another $10. I have never charged a late fee this way, I am totally upfront with all clients at interview, I need kids to be picked up on time (like others here, my own kids have activites they need to get to), and I must be paid on time. Other than that I can be flexible.
For the sticking around, yes I have that problem too. If I need to get going I will say "bye, I gotta go" and they usually get the hint. I just try to choose my battles for the most part. Many many little things annoy me, from time to time, venting on here or just hearing someone elses issues, can go a long way to ease those annoyances for me.