Eh. I'm pretty sure there's nothing wrong with "Let's." there, given that it's in response to "Can we go now?". The "go" is therefore implied. If it isn't in a different language, feel free to make it work, of course.
And thanks for going over it I'll let Zenju and Homisite know.
Qwinn
Oh, then it was my bad. I'm not very familar with colloquial English (at least, if I actually have to use it by myself ).