I wouldnt go monk depending on the age of your child. Monks are often put on pull/split duty as the game progresses and unless they get this tactic skill down they could get get the gears a bit from people. I have my son playing, he's 11 and rolled a cleric. He loves buffing people and really its sit-stand-heal-sit and just knowing to avoid overcasting.
I've found the community to be exceptional. Kind folks have gifted my boy with some better pieces of gear than I have at level 35. My son is enjoying grouping so much more here than other MMO's where one screw up or a young voice in voice chat equals immediate group kick.

Incorrect, have them only play hybrids!!!! They are the most fun afterall, just min-maxers ruin their joy!!!!

But in all seriousness, perhaps explain the role of each class with role play lore behind each archetype and let them choose what excites them most at first, if it grows too boring or complicated they can try something different.

I personally only play knights or wizards, I enjoy them and i am usually applauded what I bring to groups regardless of min-max stereotypes, though I do think the classic, kunark Era has extended too much time for the hybrid penalty. I still play hybrids non the less

I would stay off red lol