Welcome KmH, For breakfast between the southbound CS and the eastbound CZ, I have walked with my wife to Jim Denny's (12th between H & I).http://www.jim-dennys.com/
We walked east on H Street past our favorite HI Hostel which is across the street from City Hall.
Last February, My friend picked me up at the station and we checked Jim Denny's but it was closed so we went to the Denny's north of town.
There was a 24hr Denny's within walking distance of the SAC station. I have heard some bad things about the replacement restaurant.
Coming west on the CZ waiting for the northbound CS, you have the choice of many restaurants (some expensive) in Old Sacramento. I agree you should be back to the station by 9:30PM.
There are several golf cart people movers to take people with their luggage from the station to the platform if you didn't want to take the walk.
If you get into SAC early enough, you can check the luggage and then walk down to Old Sacramento and visit the California Railroad Museum. (closes at 5PM).