WOW!! are you sure you're not in my daycare cause that sounds ALOT like most of my parents.

what I do is send out a monthly letter to all parents. For what ever reason comes up that month.
i.e if your having problems with a parents with pickup time. Just send a letter out (not directed to 1 parent) but rather to everyone to say that you would prefer for all kids being there no later then 8:00 am so everyone can be on the same scehdule (YOURS) also put in the letter how much you appriciate everyone cooperation, bla bal bla...
and for drop off I never assume parents will be on time (cause lets face it---there NOT) I assume that they will be picking up by 5:15pm (my closeing) and when a certain parents is late 3,4,5,6 times (lol) i send out this reminder letter about MY closing time...