• Marvel United: simple card driven Pandemic-ish firefighting
• Quirky Circuits: Penny & Gizmo's Snow Day!: programming, concurrent planning
• The Game: hand management
• Tranquility: hand management, base game is pretty simple, comes with a bunch of expansions to ramp it up
• Dice Conquest: Dice placement, manipulation
• Teeter Tower: dexterity, balance, stacking
• The Mind: more of a silent social experience than a game. A lot of fun when you "get it"
• Kites: Sand timers. I haven't actually played this one yet but looks fun

A bit more complex:

• Pandemic: The Cure: My favorite version of Pandemic, turns the game into a dice based romp
• The LOOP: This is somewhere between Pandemic and Spirit Island, fun theme, might be a good preparation for more complex stuff
• Regicide: Only needs a standard deck of cards, not easy but very satisfying when you get a win
• FUSE: realtime, can get pretty hectic. Check theme for appropriateness.

And finally a BGG search, filtered for 10+, mechanic:co-op and sorted by rank. Tweak it using the advanced search link on boardgamegeek.