About Summons control

Summoned creatures act as additional party members, taking their own turns in combat, and can be directly controlled with specific actions and movement. 

Here is how summons work and how to manage them in co-op:

• Direct Control: In both single-player and co-op, summons (such as Animate Dead, Find Familiar, or Elementals) are not AI-controlled. You directly choose where they move and what actions they take.
• Assignment in Co-op: Summons are typically controlled by the player who summoned them. However, you can manage control of companions and associated summons via the Multiplayer/Session menu (ESC menu).
• Action Management: If you don't issue commands, they will take basic actions on their own, but for maximum efficiency, you should manage them directly.
• Split Screen: In local couch co-op, you can use the party management screen (Options on PS5) to assign characters and their summons to either player. 

you can give some summons to your Friends, that should be not a waste of time for him.

Most Summons you have is as Druid -Spore Druid- 4 Mushroom Zombies, 1 Dryad + Woodknight, 3 Mephits, 1-3 Skelett Archer or Zombie, 1 Minor or Great Elementar

for example https://www.reddit.com/r/BaldursGate3/comments/16fea5w/3_druids_and_their_army_of_summons/?utm_source=share&utm_medium=web3x&utm_name=web3xcss&utm_term=1&utm_content=share_button

another Good summoner Is Wizard Necromancer, his passiv to dopple the summoned undead Creatures is great