That will be "Is the boy here?" Russian tends to say the "definite" words first and then introduce new things, people, etc.
In fact, you can say "Здесь мальчик?" in two different ways:
- Здесь мальчик? - Is the boy here? (the default translation of "Is a boy here?" looks strange to me). The meaning is the same as in "Мальчик здесь?"
- Здесь мальчик? - Is it a boy here?
Not здець but здесь. Basically здесь is "here" and вот is "Here is..." or "Here are..." "Здесь" means "here" as the place of location of something ("Здесь пусто" - "It's empty here"), while "вот" is "here" too but it's used when you're pointing something out ("Вот твои ключи" - "Here are your keys").
It may not be proper English, but we all know how many other correct answers are not proper English. In fact, I just got this one wrong because I had a question just 3 previous that said здесь не руссиа, meaning "here is not russia", but so many people complained that they changed the correct answer to "this is not russia". So, I thought maybe this followed the same rules and I said "This is a boy". Of course this was wrong, but I'm still trying to figure out why it works in one case and not in another.