I would recommend a higher solids / higher quality product for a busy workshop like that. The type of system you are currently looking at would work OK if you were just parking cars and doing some light maintenance work.
Some of the vendors here can most likely put together a very high solids commercial quality epoxy system for you somewhere in the $1.50 per square foot price range. Most of these include an epoxy primer, high solids to 100% solids epoxy color base coat, and a high performance polyurethane top coat.
I realize that 50-60 cents per square foot adds up quickly for an area of that size, but you would be more than disappointed with the outcome of what you are currently looking at. The extra money spent will save you the time and aggravation of choosing an under performing system for the type of use you are planning for the space.