The physical game can be expensive to get into, and live tournaments can be intimidating for children, so I thought this would be a good alternative until he's gained a little bit of experience and had time to build a physical collection
Key pieces for a good Grima deck would be Strionic Resonator to double your thievery shenanigans, a good haste enabler through Swiftfoot Boots/Lightning Greaves as well as a way to punish your opponents such as Leyline of the Void or Dauthi Voidwalker
Adventure spells let you cast the Adventure spell or the creature from your hand
Hazel's Brewmaster's last ability grants only activated abilities
Sapphire & Steel: This deck, starring Sleeping Beauty and Simba, has cards that are more expensive to deploy but pack a punch
This means that you can respond to the triggers by recasting a spell with flash if it's your turn or casting instants like Brought Back to grab those permanents back to the battlefield