Is Warcaster necessary for my multiclass?

I’m trying to play a redemption paladin with 2-3 levels of celestial warlock. The warlock is mainly for cantrips, additional healing and backstory 

I was gonna play a variant human and take warcaster so I can spell cast with my sword and shield, but if i understand action economy, I could put my sword away as a free action, eldritch blast the flying enemies and pull my sword back out the next turn to attack if needed. 
if that’s right, do i need warcaster?

And if i dont, then do you have any suggestions for other feats i should take instead? Or maybe even a different race to play to get more benefits than a human?

This should work using the free object interaction (as per the Time Limited Object Interactions) to sheath should be permitted and then drawing the weapon on the subsequent turn can be made as part of the attack action itself.

This of course depends on if your DM agrees with this interpretation and may cause issues when it comes to Opportunity Attacks, Warcaster would allow using True Strike but to use True Strike you need a weapon in your hand, which you wouldn't have. So there maybe some cases where warcaster is necessary.

Notably Warcasters best feature will still be the advantage on constitution saving throws.

yeah, even if you have extra hands warcaster is still good.