A friend and his young teenage son are considering the above.

Any advice on what sort (and source) of bikes for them and, perhaps, a training plan to follow?

Cheers

I'd say you do well with one of these:

Specialized Sirrus Sport – I did 1,300 miles around New Zealand this Jan on one. Great bike, at 32h – it's probably a little bit lacking on spokes-per-wheel for proper touring loads. You might want to upgrade the rear wheel at least! Otherwise – top bike!

…as for training plans? I'd say, simply – ride! Anytime you can. The most important thing is getting used to bashing out big days one after the other, so I'd recommend training Sat + Sun for a few weeks beforehand and putting in at least 4-5hrs each of those days, together with whatever you can fit in during the week.

Get a Brooks B17 saddle and fit it to a bike that you are comfy on.
Buy a pot of Assos cream and use it often.

Keep doing day rides until your planned daily mileage doesn't cause any problems.

Pedal fast through Bolton.

One with an engine….

If you can stretch to it A Dawes Galaxy just to absorb the road imperfections. I used a Giant SCR3 with an upgrade of Mavic Kysirium wheels. Never shed or broke a spoke where as the two other lads running standard wheels snapped spokes.
A good set of carbon forks and some good quality bar tape or grips depending on what typr of bar set up is also essential. As for mileage if you can crack three days in training of 70 miles a day you will find that the rest of the dyas will just tick by with few problems.
Oh and Assos bibs shorts/longs and good quality chamois cream, and a camera-best days of my life……..

Thanks for your help fellas; I'll steer them to this thread.