I agree with the other poster about respecting subclasses and considering multiclasses. You’ll want someone who can take hits on the Frontline, and put of those four it’s yourself and Shadowheart that are getting volunteered for duty.

Shadow can get heavy armor from another subclass. If you want her to blast a bit as well as support, you could always consider Tempest Cleric 2/Storm Sorcerer 10. You get heavy armor from the dip but and can use the Channel Divinity to max Lightning Bolt. She can also twincast Haste and then Quicken another spell at later levels. She’s a nuke but needs long rests. If you wanted her to be more martial, you could instead go war cleric which gets extra attack at 5.

My MC is a Warlock 5 / Paladin 5 / Storm Sorcerer 2 (I know it’s suboptimal, but I want the free flight from storm sorc). The extra attack from Pact of the Blade stacks with any martial extra attack, so at level 10 you’re dishing out 3 attacks per round using your charisma mod instead of strength or dex. I started with a level in Paladin to get Heavy Armor and weapon proficiencies, as of you multiclass in later you only get medium armor. It’s kind of immaterial as you can respect, so if you just want to start as a blaster lock and respec once you have the levels to do so that also works. I was definitely gimped early game by building almost entirely around CHA, dumping STR and DEX a bit, and still hanging out in melee. I built my lock to use Polearm Master and Sentinel to help control the battlefield, but you could run a shield and one hander for more survivability. Or go Great Weapon Master with whichever 2-hander you run across and dump massive crit smites, 2 per short rest minimum, burning your character level scaling warlock spell slots.

The most important thing is to remember that nothkng is locked in. Keep respecing and experimenting until you find something that works.