I know I can create a new kernel for my notebook from the evaluation menu but is there a command for this? I'd really like some of my notebooks to startup their own kernel as the first line of code.
Ok, so first of all you have to be aware that number of kernels you can use is limited by license.
You can go now to
Evaluation -> Kernel Configuration Options and create a new one, let's say
"Kuba". It will stay on the list for future too.
Now you just need to evaluate in your notebook:
SetOptions[EvaluationNotebook, Evaluator -> "Kuba"]
and this option will be saved in it too so no need to evaluate that line each time.