Some of these points have been covered , but I'll go over em again.
You've made it far too complicated.
Get rid of the unmanaged switches , just run the wires.
A managed switch , while preferable , is not necissary in this application.I would suggest something like a 'semi-managed' (web-managed) switch....they will cost a lot less but still provide the extra functionality you might need.
What kind of router do you intend to use ?
As this is a business , I'd suggest something a little more robust than yer average 'off-the-shelf' home router.....Something like PFsense/smoothwall etc.
As far as cabling goes : I don't think you need cat6 , but as jdrom17 suggested , look into 'STP' cable , especially if the cables are being routed next to AC power/fluorescent lighting etc.....