Apple allows you to determine a release date. I’m not sure if Google Play and Amazon do the same thing, but if they do, then you can have all your apps released the same day, but honestly, you may not necessarily be in control of the time. Each store has X number of hours before your app goes live anyway depending on how fast their index servers can work (this can take hours). It’s easy enough to open three tabs, login to each developer platform and launch, switch tabs, launch, switch tabs, launch and release them with in a few minutes of each other. Again indexing them so people can find them is a multi-hour wild card to a point where a few minutes isn’t going to make a difference.
It reminds me of a quote from an old Murphy’s Law book I used to own:
“Measure with a micrometer, mark with chalk, cut with an axe”.
The point, why worry about precision when the final tool is wildly inaccurate.
You might want to google “App Annie” and use that to get you started on finding an Analytics Service that can collect stats from the various developer platforms together. You will have to grant them accounting access to your profile, something people may not be willing to do.
Rob