First, let me just say that you don't need a high Charisma character to enjoy the game. You'll find that there are a lot of different skills that lead to interesting results other than just persuasion, intimidation, and deception. With Background, Race, Class, and your other skills, there will be very few conversations that won't include some special interactions.
That said, I strongly recommend that your Main Character be the one having all of the conversations. One of the main ways to build trust/relationships with your companions is for them to watch you interact with the world. If you continually have other characters speak for you, you'll lose out on all those "relationship points" (for lack of a better term).