Stephiej - thanks for thinking it through and replying. Sometimes we provide feedback and *poof* the OP is gone!
Your reasons for trying the protein powder make sense in a way. But some considerations. The money is already spent, you won't gain money back by consuming it. Sure, the food you buy as a replacement will be the added cost, but a few sweet potatoes, cans of tuna, or chicken doesn't cost that much.
What Brewer5 said- change your definition of convenience. I like it! Convenience foods got many of us into the sub-optimal health situation we were in before Whole30. One goal of the Whole30 is to help with that redefinition.
One thing I do to save time is prep extra servings of a recipe and make it specifically for pre or post workout. So if I'm making a chicken dinner, I'll leave a few portions out of the sauce/fat/spice and leave them plain. Microwave a potato, throw them in a container to have ready after a workout. That way there's no 'extra' time involved. And without the extras on the chicken, it's pretty finger-food friendly.
You are post-Whole30, you can do whatever you want with the protein powder, but to make it the first thing you excitedly jump back into...you can do better
You've put some good thought into this, just keep thinking, you can find alternatives to test and see how they do for you. Then think about the powders again.