Fixed wing should be fine. Magnets tend to only mess with stabilization stuff like gyros/accelerometers but always test for your own peace of mind. Do a range test without the magnets, then add them where you want to locate them as a final product and re-rangetest.
An electrical current moving in a wire will generate an electromagnetic field. The EM field consists of an electric and magnetic component. If a piece of ferrous metal is near the wire when the electrical current moves in it, the metal will have a force exerted on it by the magnetic field. Additionally, a current will be induced in it. This basic principle is how a motor works (using the magnetic field to do work) and how RF communication works (using the electric field to induce current in a receiving antenna).
A magnet moving relative to a metal object will generate a current in the metal object. This is how a generator works--same principle, but in reverse. But here's the key: if the magnet is stationary relative to the metal object, no current is generated. Therefore, as long as your magnets are not spinning around (for example), they're probably not going to generate interference. Bear in mind also that your antenna wire is coaxial cable specifically to help with rejecting induced current from fields like this. If you were to spin a magnet around inside a loop of coaxial cable, most of the induced current should be carried by the ground sheath, leaving the signal relatively unaffected.
Referencing the above, there ARE already magnets on your brushless motors, and we don't seem to have too much issue with excess current generation with those. So, the magnets are probably fine, so long as they're sized within reason (it doesn't take much to hold a hatch shut).