Q: Please note, the heavy beard is on my husband's chin, NOT mine! *lol*
A: to shave it off? or to maintain it?
just any electric beard trimmer should be able to trim his beard. if he wants to shave it , you can just use scissors and then shave it manually
You should consider the philips range, the three headed ones. they are designed for people with thick and course beards because they are more aggressive, so it will cut through better. philips have a new range out called "Sensotouch 3D", it is abit pricy, however it is worth it in the long run. excellent quality, because it is made in holland, depending on where you are from, you get a 60 day trial, so if yur son is unhappy with it for any reason you can actually get ur full refund back from philips. in the sensotouch range, you can actuallly use it in the shower wet and dry, they actually improved the blades, which accomodate for long, medium and short hairs. and there is full 360 degree flexibility, and the heads can go inwards and outwards to accomodate for curvatures of the face. it is also best he uses a shaving cream/oil befre he shaves because that actually softens the skin and lifts up the hair allowing for a better and more comfortable shave.
hope this helps