If you have the time I would do a stepped starter in the 2L flask. That is making a starter, letting it settle, pour off the liquid then add another batch of starter wort. It will take a few days.
is the best site I have found for calculating the size of stepped starters.
If you don't have time I would probably make the wort and put some in each flask then estimate the amount of yeast in each as best I could. I don't think it is critical to the final yeast count to get it exact in each vessel.
If you sanitize really
well mixing in the pitcher would be OK.