English Advice?

I teach English every Friday and Saturday to adults, with an English-Japanese exchange every Tuesday and a monthly visit every first monday to a day care to sings some English songs. The day care is a bit of confusion especially when the teachers do not understand a single word of my native tongue and I only a few of theirs. But we manage together, which is very helpful. If they had left me alone with 30-something children under the age of 6 I... would probably not do so well, haha. (Actually, I'm not so bad with kids and when we can both communicate effectively I am fine supervising kids. It's that darn language barrier -shakes fist- )

There are some times, though, in the adult class when they ask me a question and it stumps me. I can easily look up a word in my handy English-Japanese dictionary that I pirate away from my husband on the weekends because it has an English dictionary for English people in it as well. But when they ask me the why questions, that's where I have trouble. One of my students even told me that he could understand every individual words meaning but he couldn't understand the sentence meaning. Sometimes in English news or books I will have to read it over again because I do not understand the point they are trying to make in the sentence, but 80% of the times it is due to the fact that I will have skipped an important word. The sentences I use in my classes aren't terribly hard to understand - At least from my point of view- But sometimes I forget that they are learning the language, and just as I have a billion questions every time I study Japanese so do they.

Although is it too much to ask for a vocal response from them when I ask Does everyone understand? Does anyone have any questions? Because when they sit there re-reading what I have explained I cannot tell if they do or they don't and my instinct says Well if they aren't asking questions, they must understand.