Yeah I actually forgot about the monk extra attack, haven't played a monk in awhile. But the more I look in to it, the more I see why you'd wanna go monk/sorc. Here is how I would play it. The only thing I'm conflicted with is either go open hand or elements with monk. Picker's choice I guess.

I would go as black dragonborn, kill Karlach for Infernal Robe from Mazora and have cold ancestry, it can be whatever ancestry you want, I'm just saying. That would be poison, fire, and cold resistance all at once. It looks pretty interesting.

Level 8 Monk, Level 4 Sorcerer

Stats
STR= 8 + (+2 Stat Potion)
DEX= 16 + (+4 Ability Improvement)
CON= 16
INT= 8
WIS= 15 + (+1 Hag Hair)
CHA= 10

Feats
Ability Improvement (+2 Dex)
Warcaster
Ability Improvement (+2 Dex)

Class
Sorcerer - Draconic Bloodline
Draconic Ancestry: (Choose Resistance)
Metamagic: Distant Spell
Metamagic: Extended Spell
Metamagic: Quickened Spell

Cantrips
Blade Ward
Ray of Frost
Fire Bolt
Shocking Grasp
Friends

Spells
Shield
Blur
Misty Step
Enlarge/Reduce
Mirror Image


~Kensei~