What is the right way of connecting 2- 12volt batterys together to make a 24 volt system, is it neg to pos,
Yes.
can it be charged with a 12 volt charger while still being connected as a 24 volt system because it will be a sealed system
Probably not---the "12" volt charger puts a slight over-voltage across the battery(Around 15 Volts), so it won't charge what is effectively a 24 volt battery.
Why not use a 4 or 6 mm gold plated male/female connector between the two 12 volt batteries, like the electric flight people use on their power packs?
They're tough and simple but reliable to connect/disconnect, and you should be able to charge each 12v. battery in turn.