Kids addressing older people

Solution 1:

In UK schools, female staff of any role (and any marital status) are universally addressed as "Miss". Just that; nothing else. It would definitely be wrong to add the first name ("Miss Daisy") as that's too familiar, and "Ma'am" or "Madam" would be seen as insolent because it's too formal.

"Miss" the equivalent of "Sir", the generic mode of address for male staff. "Miss" is akin to "Ma'am" in the Forces, where "Sir" would be used for male superiors.

When referring to staff rather than addressing them, the full name is usually used. "I gave my homework to Mr Jones."

A janitor is known as a caretaker.

Solution 2:

If the boy knows the woman's name, it would be appropriate to address her saying it. Miss Taylor, for instance. If he doesn't know the woman's name, as I presume to be the case, "Ma'am" or "Miss" (even if she is married) would suffice.

Solution 3:

If the child knows the woman's name, he will typically call her "Miss Brown" or "Mrs. Brown" or "Ms. Brown", depending on her preference. (Assuming her name is "Brown", of course.) As someone noted earlier, in some contexts, where she wants to be less formal, he may call her "Aunt Sally". If he doesn't know her name, he will call her "miss" or "ma'am".