This is an interesting pattern. One asks for permission, and permission is normally given. The answer is therefore はい or ええ. In English something interesting has happened: instead of asking for permission, we tend to ask if we are able to do something/if we have the ability to do something. We ask in spoken every-day language, "can I have a drink, please?", although we mean "may I have a drink, please?" In Japanese this mistake is not made. Don't ask anyone if they think that you have the ability or skill to go to the toilet - they will either burst out into laughter, or they will look for a nurse. May I go, please?
The pattern is：
the ～て form of the verb plus もいいです.
"... Not just now, boys...
Maybe we can all go later?!"
