That's a generous tip, as far as tipping bus drivers. Perhaps we're cheap, but for a bus driver, who merely drove the bus and unloaded our luggage, I'm fairly certain hubby only hands him a $5 bill.
And that would be for the somewhat longer drive in Orlando. If we were in Miami, it would be just a dollar per bag.
In San Juan our bus driver from airport to pier, gave us a running commentary, semi-tour for the whole 30 minutes. He was quite entertaining. He got a good bit more.
BTW, I'm always surprised at how few of the shuttle passengers tip anything at all.