Can I start L2 dependant visa stamping process for wife and kid together or it has to be one after another

I have an approved L1-B visa stamped on my passport and planning to travel to US next month (June 2016). This time, I am also taking my wife and kid (5 years) with me on L2. I understand for kids less than 14 years, there is a visa waiver program (dropbox) option available and hence only wife needs to visit VAC as well as attend visa interview at consulate.

Should my wife first finish her visa stamping process and get a visa on her passport ? And then should we start the process for my kid using the visa waiver program (dropbox) option ?? I guess If I take this approach, both me and my wife will have visa stamped and its going to be easy for the kids process. I am doubtful if I start the process for my kid also (along with my wife), only one of the parents will have the visa stamped and it may create additional processing/concerns for kids visa stamping. Please share the thoughts.

It must always be done together when possible. It shows confidence in your paperwork.