The newer models use a different stereo than my 2011, so I can't speak of the connections available. My unit has an Aux2 jack on the back--had to take the unit out of the cabinet to get to it.
As to mounting rigs, think about making a removable cabinet that would straddle the gap between the front dinette seats. Lots of folks--myself included--have made or bought smaller tables; that would make some room for a radio setup.
It's never too late to have a happy childhood!
Lee, WU0V, and Courtenay, N0ZDT
2011 Rockwood A128
2000 Silverado 1500 pickup
60W solar system
2000W inverter generator