Since you have the Str, no need to go hexblade. I would dip fighter for heavy armor and defensive style, or cleric for the spell slots. And then take +1 Str / +1 Cha, +2 Str, +2 Str, and resilient Wis. Possibly inspiring leader.
You will end up with 26 AC. 18 heavy armor, +1 defensive style, +2 shield, and +5 shield spell.
+3 Cha will still be enough to cast the occasional fireball, which does half on a miss anyways. And spells like greater invisibility and haste don't require Cha.
I actually thought about dipping into Paladin as well after looking around for other ideas. You can't get Heavy Armor proficiency from dipping into Fighter though, only way to get it without taking the feat is to dip Cleric and take a domain which gives it. So "only" 25 AC instead
