Kit will be taking a level in Warlock. As Len said, multiclassing has its own risks and rewards. I've multiclassed a) because the story called for it, b) because I wanted to max the powers from two classes, and c) because I wanted to mimic the abilities of a fictional character. Sometimes the two classes work together in powerful ways. Other times, the character ends up being less powerful than if he had stuck to a single class.
First off, with multiclassing, you have to make sure you have the minimum score (13) in the class's primary ability. In this case that's not a problem since warlock and sorcerer both use charisma. On top of the abilities of the new class, Kit gains the new class's hit die and certain proficiencies. Not all of the proficiencies of the new class, just certain ones. And when I was looking up the hit dice, I realized I had given Kit the wrong HP. A sorcerer, like a wizard, uses a d6, not the d8 I had used (sorry, Len). A warlock uses a d8. So instead of having 2d6 hit dice, Kit now has a d6 and a d8, either of which he could use to regain hit points during a short rest.
The proficiencies he gains are light armor and simple weapons. The simple weapons don't add much to the weapons Kit could use, but the light armor? I'm looking forward to finding some studded leather to add a couple points to Kit's AC.
Multiclassing as two spellcasting classes gives Kit a tremendous range of spells to choose from. Typically, though, when multiclassing involves two spellcasting classes, the spell slots don't stack. For example, a 1st level bard/1st level cleric gains the spell slots of a 2nd level character, not two 1st level characters. Because the warlock class works differently than other spellcasting classes, Kit, however does get the spell slots of two 1st level characters, and he can use the spell slots from either class to cast spells from either class. Once Kit gains a couple more levels, that's going to give him a tremendous advantage since he will be able to convert his warlock spell slots into sorcery points and then regain those spell slots with a short rest.
This advantage of regaining expended spell slots from a short rest is tempered with a low number of spells and spell slots. Kit only gains one 1st level spell slot and two cantrips and two spells. For the cantrips, he'll be taking Eldritch Blast and Frostbite, allowing him to help out more in combat. For the spells, he's taking Sleep and Arms of Hadar, both of which operate on multiple targets.
I'll be taking the average hit points for a Warlock (5) and will roll a d8 to gain some HP during our short rest.