You can go from the easier concepts to the more complex stuff.
Believe it or not many people say that know the verb "go" but when you make a sentence with "went" they don´t recognize the pattern.
There are good books with hotel and traveling lingo, but don´t forget to wedge some of the grammar of English in the conversation.
Don´t forget to check their English pronunciation (you can get that by making them read something as well).
Usually some letters like "a", "ee" (togheter), the way the stress the syllable (I mean rhythm) is different from Portuguese, that might be checked and corrected. Here is the short of it, there are lots of other details, but I will leave to the real experts, more advanced learners or natives to comment.
And, one more thing, you are in touch with English but don´t forgo some details of Portuguese, so you get cred as a teacher. I wish you luck in your new path - lecionando para alunos de inglês.