What I did was just setup everything as wireless. If your office is small enough then just check the signal strength in the different rooms. The advantage is that you wouldn't have to bother running Ethernet cable and it gives flexibility in moving things around. Just make sure you setup security properly.
You never really asked a question, but I assume that you're asking if your setup is O.K.? Are you using a home/small office routers? If so, I don't really see the need for separate switches for only 4 desktops since the home/smb routers have built-in switches already. You could connect router to router if you so desire.
I think to fully answer your question you need to give more detail such as size of the office, what kinds of apps they'll run, etc.
Lastly, regarding file sharing, if you have a spare small pc, you can just set that up for people to share files on instead of getting a whole server. For only 6 people there's not really a need for that unless there's something you need to run like a DB. The office I setup I just connected a spare PC they had to the router and enabled file sharing, then mapped a drive from the PC's to the spare share.
P.S. Another thing I just thought about in your proposed configuration using the switches is that you create a bandwidth bottleneck by connecting the switch to your router, then having your users connected to the switches. It's better to just have them connected directly to the switched ports on the router.
