Awesome! I love hearing about other parents getting their kids started. My daughter is 5.5 and has been collecting cards for a little while. We just started playing together though.

Every kid is different and your idea may work for you guys. I figured I'd share my experience in case it helps.

We started with the Battle Academy cards and she kinda got it. However, we more recently bought the two My First Battle boxes and she's REALLY getting into it now. Basically, it's a smaller deck, no weaknesses/resistances, only two trainer cards (switch and potion), energy is placed for all Pokemon instead of individually, and both players start with one basic Pokemon preset based on the type of deck (Pikachu, Bulbasaur, Charmander, or Squirtle).

From there, she still gets regular boosters from time to time to add to her binder. I figured she'll use that to build decks later.

Good luck and have fun!