I need some advice?

A job opportunity just came up for me to be able to bring my daughter (3 this Sunday) to work with me. I'm currently 11 weeks pregnant. I've already been interviewed (way back in August - before conception), and everything is set for me to get "officially" hired and start working.

We haven't announced that we're pregnant to anyone yet, but plan to at/after Christmas. Is it wrong of me not to tell this company that I am right now, or is it acceptable to wait? This baby would also be coming to work with me as well.

I know you don't have to tell them you're pregnant, and part of us isn't ready to announce yet, but part of me feels as though it's wrong not to give them a heads up. My daughter will be starting preschool next fall, so it would really only be both of them there with me for about 2 months.

Also, one of the higher ups (not a boss, but he's up there) and his wife (literally work together) bring their 4 daughters and homeschool them at work as well.