Whatever you pick, I'd suggest asking the shop to do a trade-up to thorn-resistant inner tubes and at least some 2.1" tires if it doesn't have them already (reason: TR tubes are very hard to pinch-flat, and big tire casings are harder to bottom out on rocks and curbs, which helps prevent dented rims).
If the bike comes with a rear wheel that has a non-freehub design, the shop can probably upgrade the wheel and cogs to a freehub for a reasonable price at the time of purchase, and sell the original wheel later for a repair. Freehubs have the driveside axle bearing near the end of the axle, greatly reducing the likelihood of axle breakage. While they're at it, ask for an estimate to convert to a base-level Megarange cassette and rear derailleur, if you think your bro-in-law would benefit from an extra-low gear. Probably wouldn't cost too much after trade-up allowance on the stock freewheel (or cassette).
If he can afford to do it right the first time and get it over with, I'd have the shop hand-build a very strong rear wheel for him: DeoreLX hub, 36 DT or Wheelsmith 14ga spokes and a Sun RhynoLite rim, with dummy spacers to run 7sp cassette if needed.
I had a nice mentally-handicapped customer who rides and rides and rides, with a huge basket over the rear wheel for collecting scrap metal. He happens to be about as big as your bro-in-law too, and this wheel has really paid off in the long run for him, compared to the $50 basic alloy replacement wheels he was going through. With trade-in allowance on a typical stock wheel, this is about an US$80-90 upcharge by my figures.
Last edited by mechBgon; 07-26-02 at 12:51 AM.