I talked to my dad, who logs about 7000 miles a year on his bikes, he got into cyclocross a few years ago, and knows way more about it than I do; hope this helps ...
A few things off the top:
Cyclocross bikes are built similar to road bikes and have handlebars and brake/shifters like road bikes. They are built for fairly light off road surfaces - trails, dirt roads, grass, and not for heavy duty single track, rocks, or drops.
Cross bikes have tires that are about half the width of mountain bike tires, and tires that work well on roads do not work great on dirt and visa versa. Ride with very low profile tires so you can go reasonably fast on pavement and still have some traction off road. He might be better off with a couple of sets of wheels and then spend one day mostly on road, and with a knobby set, go mostly off-road on another day.
All the major bike manufacturers have seen an explosion in demand for cross bikes and now have models. Redline makes decent bikes at good prices. So does Independent Fabrications at higher prices.
Go with the clipless pedals, Shimanos with dual entry are great. So are Crank Bros. p