Unhappily, the people I know who use Whatsapp were not at the training session on Tuesday so I went and installed Genymotion on my own computer - out of curiosity as much as anything else.
It's quite a big install, the whole thing including an emulated tablet and a smartphone came to close to 500 MB but I have to admit it seems to work quite well. But to get back to your original question.
It might be possible to write a batch file to run at start-up to make it load but I don't have the skill or knowledge to do this and I suspect from what you said earlier neither do you. In which case you are left with starting it up, selecting your appliance and running it.. But you don't have to shut it down each time you want to do something else on your computer. All you have to so is minimise it to the taskbar by clciking on the left hand of the three buttons in the top right hand corner of the emulator - the one that looks like an under score. Then the next time you want to check Whatsapp - or anything else - just click on the the entry on the taskbar and it will come back to full size.
I know this isn't what you wanted to hear, but I hope it is of some help.