Old Sac, in its current state, is a Bourbon Street wannabe.
Which isn't to say Old Sac isn't worth going to. The Railroad Museum is great. In the summer the KCRA sponsored free jazz concerts are terrific. You can buy a glass of local wine there, eat at one of the seafood places, or bring a picnic and it is very enjoyable. I like parking a mile away at the water exhibit on Jibboom Street and walking in to Old Town via the Sacramento River Trail. (It isn't pretty, but it can be interesting.) I often walk my dog to the waterfront there and just watch the boats and the people.
I'd say put Old Sac on your list, just know that it isn't one of the cool Gold Rush Towns, that it is incredibly cheesy, and that it is Sac's biggest tourist trap.

