I dont have one of my own yet (winter project) but it seems that most people will tell you that soem sort of custom 4 link type suspension (gecko from rcguy.com for example) with tamiya Clod Buster axels/gearboxes will make the best RC Crawler.
They will also tell you that the Tamiya TXT-1 is also a pretty capable crawler out of the box (and then they will argue amongst themselves whilst they decide if the TXT or CLOD/CUSTOM is the better. The Clod usualy wins because its motors are both fitted to the axels giving very low CoG... but the TXT has the edge because it is all in the same box to start with and is a little more suited to a beginner.)
Then some guy with an e-maxx will show up claiming them to be the best crawler since <insert comicaly good crawling thing here> and then a bunch of guys will jump on him because the e-maxx has wishbone/independant suspention, rather than 4-Link and then they will start to argue that Articulation is God when crawling... then the e-maxx guy leaves to get pictures of his e-maxx getting 11" of suspension travel.......

If you survive all that and ask about electrics you will get a thousand and one suggestions for a good reciever/transmitter (Rx/Tx) combo, but nearly everyone will agree that the Novak SuperRooster is the only ESC to consider and that Integy 55turn Com-Late motors will probably be the way to go. The integy motors are designed for A seperate application all together but they produce huge amounts of torque (which is the be all and end all in crawling - apart from Sacred Articulation of course ) .

Which leads me to my final point... It seems to me that unless you really want to slowly clamber over technical trials type courses Rock crawlers are pretty specialised. And as these things generaly have a top speed of about 5 mph they arent very exciting with nothing to climb... so the first question is wether it is really suited for your nephew... crawlers are almost the polar opposite to most nitro trucks...