Do you have a contract and handbook with these things spelled out? Because I do know that sometimes we as providers have trouble enforcing our policies. If you do have a handbook and contract then start following it. And if you dont, then make one and have all of the parents sign each page.

this is your business and you get to make the rules. If you dont want them just walking in then lock the door. And if they dont like you locking the door, then they need to find care elsewhere. If dckid is not there at set meal times then dckid does not get that meal. And if you dont want him arriving in the middle of preschool time then tell them "no arrivals after 9am".

Make the policies and enforce them.