I got fined at Liverpool airport for dropping my wife off on the road, but this was a few years ago. £60.
You're welcome to leave your car round my place, but being over a hundred miles from Manchester Airport might present problems of its own.
Just check there’s no train strike that day
£5 to drop off and pick up. But you have 5 minutes, so tricky on pick up, unless he parks away from the airport, awaits your call to say "outside now", then into the Terminal like a F1 pit stop, then out ! You can do short stay parking which is a little more expensive and gives you about an hour from memory.
We just get a taxi now for about £35-£45 from 10 miles away.
You can if you want to risk it have your son assuming he will also pick you up, park outside the perimeter, then when you land you go up the escalator to the departure level. You call your son, he arrives at the departure lane, you get in & you both drive away OR at least you used to be able to.
For 10 miles
Think it's up to £100 now at Speke.
However there is now a free short stay there, the exit off the roundabout before the big car park, think you get about 40 minutes from memory.