Party with Bard (Jester) and Sorcerer but no Mage viable?

Hi - because of a certain, ah, new addition to the game, I'm thinking of adding a Sorcerer to one of my current parties, but that means removing one of my current NPCs either Kagain or Neera (decided to have a change from Edwin). I know, however, that Sorcerers are not as flexible as Mages and don't have such a large spell selection, BUT, CHARNAME is a Bard (a Jester, in fact), so I do have another spell-caster. I quite like Neera, but am thinking of removing her from my party when I've done her quest(s?) and met a certain someone. The alternative would be to remove Kagain, but that only really would leave Dorn on the front line, as I dualed Shar-Teel to a Thief at Level 3.

Will my party still be viable with a "proper" mage, if I have just a Sorcerer and my Jester?

My current party is:

Dorn (Blackguard)
Kagain (Fighter)
Viconia (Cleric)
CHARNAME (Jester - Neutral Evil)
Shar-Teel (Dualed Fighter/Thief)
Neera (Wild Mage)