Your wife and children cannot apply with you as a dependent as there is no dependent allowance for long stay category. Detailed information on this is here;
http://www.immigrationboards.com/viewtopic.php?t=105162
However once you get your ILR, she can become your dependant using FLR application. I am afraid she needs to stay 5 years in this category before she can apply for ILR. This may very well delay the total time she needs before she can reach to ILR herself. If she is becoming eligible faster on her own capacity as a tier 1 migrant herself, she may do it on her own without becoming your dependant first. Because since she is becoming your dependant for the first time after you get your ILR, my understanding is that she will be subject to the new immigration regulations. If she had been the dependant and you had been the main tier 1 migrant, this would have been much easier, as she would be subject to the old immigration rules.
I am unsure about the child but I think as soon as you get your ILR an application for the kid can be made for citizenship directly. You may want to confirm this bit by doing your own reading.
Nobody will need to leave UK for switching their migration category as they seem to have a plenty of leave to remain left until September 2013.
