@OCMD , what to get really depends on what your kid wants to do with / focus on, what you already have and how much you are willing to spend.
The mavic is rated to have a camera almost as good as the dji phantom 4. I have a dji phantom 4, since the convenience of a smaller package like the mavic doesn't interest me I won't be buying a mavic. The big down side of the dji v. The go pro karma is that the dji cameras do not record any sound because they don't need to in flight where all you'd hear is the beating/more of w buzzing of the rotor blades. You could still use the copter/gimbal and camera as a hand held unit like
@biffdotorg does but you would have to add sound in later during the editing process which is bound to add time to the same. The mavic without the remote is is $750, I would opt for getting the remote which is another $250 and at least one extra battery which are suppose to be a little over $100 each. So all told the cost of a mavic plus a second battery is $1,100 plus tax. One other thing to keep in mind is that the mavic is a purpose built / dedicated flying camera with a lot of advance flying features and capabilities that the karma simply doesn't have (e.g. Obstacle avoidance, altitude maintenance, redundant GPS systems, accurate object tracking, etc.).
As a far as the go pro karma system is concerned it is a very versatile. Small folding yet capable quad copter , remote and removable gimbal but the camera is sold separately if you don't already have a gopro 4 or go pro5/session 5. If you want an all around system that you can use in the air or on the ground with sound recording capability and electronic stabilization the karma seems to be the only option. Again the copter functions don't / can't compete with the mavic but if arial photography / videography is only part of what you are after the mavic isn't the best choice. Cost, $800 without the camera. Not sure what the batteries cost but they are inexpensive for the cameras so maybe they will be for the copter as well. If you buy a gp5 with the karma add $300, $200 for a session 5, $400 and $250 ish respective if you buy afterwards. I'd go with a gopro 4 silver since it has a screen on the back which would be useful for framing shots when using the hand held gimbal, it should also cost less than the gp5 as well but if it's not around $200 you may as well spring for the gp5 at the time of purchase.
FYI- After a lot of thought, I've decided not to buy either the karma or the mavic. I haven't been using my quadcopter much but have been using my gopro a lot. If anything I may pick up the go pro gimbal. By the way, I'm still selling my p3 advance but the used market Is now flooded with them as well as the standard and pro models. I've seen some p4s for sale as well but the prices for them are still up there by comparison.
