Hi Dave BIG welcome to the forum,you will have a fabulous time and it is a good idea to plan your time whilst you are there to get the most out of it.The Hummer can be hired through here

http://www.uscarhire.co.uk/prestige-...e-florida.aspx

Not sure about the Harley though,there are plenty of things to see and do as well as the theme parks,Miami is on our next must do list as is Daytona.The space coast is also a great place to visit with the Kennedy space center as well as Merritt island national wildlife refuge (well worth a look) and also Cocoa beach (fabulous)
Happy holidays[8D]