As stated above, boots always come first. Nothing else matters if your boots suck.
Hunt down that proper set of boots, and use whatever leftover cash you have to get a board and whatever else he may need.
A lightly used board is perfect for a light, little, growing ripper too. If someone's already gone to the trouble of breaking in a board, he'll have a better first day on it. I'm not a big fan of "weight determines board size", other than the fact that the 156 is more than likely way too big. It's still ridable, though. And crappy boots will make every day on the hill crappy. So boot up.
Also, be looking in the softer range of boots based on his weight. I doubt he's got really strong legs. Stiffer boots typically make riding miserable for lighter, less seasoned shreds.
Boots of choice around our shop are the Thritytwo Lashed and Celsius Cirrus. I'm an all-mountain bomber, and rocked a pair of Thirtytwo Prospects last year while on the bunny hill teaching a snow bunny. Something in the range of the Prospect will probably do him right - comfy as hell, medium-soft, break in great, and he'll get at least a season out of them. The softer boot means he won't be using strentgh to work the boot. Rather, the boot will work with his feet and legs more for longer days on-snow.