First of all, these times are wildly inconsistent, which suggests the kid needs more race-pace intervals and tempos.
I'd like to know a 10k time so we can understand his strength, and maybe a 400 just to get a sense for his raw speed (hand timed will do, but FAT is preferable, as you know).
Get back to us with that obvious information and I'll give you a reasonable goal time in the marathon, and write a good schedule to prepare him. London is a bit soon, but maybe we can target Berlin this fall? I'm thinking 80 mpw should be good for this first time out, but we'll need lots of marathon pace work.
In the meantime, take him to the track and have him do 1000s and 1600s once or twice a week. I'd like to see, for example, 6x1000 at his 5k pace, with 1:30 rest or so. Please send a video of this.