Mixing models. Is it okay?

[darwin-t]

Can the following quads be flown in close proximity at the same time?

FC40 with 2.4 Ghz FPV
Phantom 2, which I THINK is the opposite. I'm not sure exactly which model it is
Walkera 2.4 Ghz, no FPV
Flamewheel 550 2.4 Ghz, 5.8 Ghz FPV

 

[OI Photography]

As long as the radios used on the Walkera and the 550 have frequency-hopping technology, like most do these days (including DJI's), you'll be fine