This is great advice. To be more specific, you only want to take a couple rogue levels. One at level 1 and one to 'catch up' skills much later (usually right after you hit a nice spot in the ranger levels and normally no later than after ranger 11 but it definitely be earlier...I've even seen some take it at level 4 after ranger 2 to get evasion as quickly as possible).
If he's going to solo on occasion and wants a halfling a dex-based light monk is outstanding. The saves are great and the ac is phenomenal. On that one you'd want at least 12str, 16dex, 14con, 14wis. That takes traps out of the picture of course but it's another choice on a reroll. They can normally keep themselves alive with their healing finisher thanks to outstanding defenses.
Finally, if he decides to play a robot then having a wf'd wizard would be great. Honestly HE could play a wf'd wizard/rogue too if you get right down to it. It gives you traps, buffing, and at low levels melee too! You take rogue at level 1 & 9 and wizard every other level. Set yourself up at level 2 with shield, master's touch, and expeditious retreat running, get a nice 2-handed axe, and go to town. 14str,16con,18int, dump everything else for a 28-point build. 32-point builds I'd just toss in more con. If you both go robots and one's a rogue/wizard then I'd make the other a sorc. More sp's than the wizard so they can be the 'healer'. Again, we're talking low levels so you don't have to worry about tanking raid stuff or anything like that and I can still go toe-to-toe with stuff at level 10 with my rogue/wizard thanks to the docent from Update 5 (+3 docent with invulnerability and lifeshield).