i work a 40 hour week MOnday -Friday. they have just told me i have to work saturdays also AND only gave me notice today and my wife works weekends so i said i was the only one to watch my kids and they told me i had to bring my kids to work. there's no way i will get any work done with them there as they are age 2 and 3. is this legal?

It is not illegal to require you to work more than your usual schedule, even if it requires overtime (two states have limited exceptions on how much overtime you can work and yours is not one of them and you would be no where near the max hours allowed by either of them).

You are lucky that the employer did not insist that your children not be brought to the office and that you make child care arrangements that would let you work without the distraction. That would be legal, too.

It is really nice if an employer can give advance notice of the need for overtime, but not always possible.