Need some ideas for decks for young children, that's better than the Battle Academy.

I got back into the game after 18 years, Having a great time. My nephew and niece, 5 & 7 respectively, have recently started to play and they started with the battle academy. They appear to be ready for something slightly more advanced instead of just play cards. I kinda suck at deck building currently and my idea of 'slighty more advanced' may not match with them. So I want something with a core strategy but simple enough for them to understand and use their brains a little more. I would definitely prefer the decks to stay monotype. Anything would be helpful.

Edit: Thanks to all the helpful comments. Wasn't expecting so much feedback. Most are saying to go with the Battle decks. So that's prolly where I'll start. And some were suggesting just throwing the kids in the deep end and give them some meta decks to play. I kinda sway here on that. And maybe it's my Yugioh side of my brain talking to me, I don't want them to be overwhelmed and not having fun with it. Hopefully in a few months we can get to that point of throwing them into the deep end. Thanks again for all the suggestions and feel free to keep adding more in here for others who could use the information.