Quite some time ago, I toyed with making the D&D iconics for M&M.
The builds started here, with Jozan,
The Atomic Think Tank • View topic - Set's Sideways Supers (Wild Cards; Swarm character)
and went on to include Regdar, Naull, Kerwyn, etc. as well as racial 'containers' for standard D&D races (dwarf, elf, gnome, halfling) and some non-standard races (changeling, shifter, warforged).
Using pregens would likely be fun for an introductory game, and mix it up by allowing different kids to play different characters in different rounds (round two, everybody get up and move one seat to the left!), so that everybody gets to see what a fighter, wizard, priest or rogue type build can do, and figure out which one they enjoy most.
Once any particular kid (or totally new adult player) is 'sold' on a particular character type, they can then be encouraged to suggest tweaks to the character, such as weapon type or preferred spell types or whatever, and you can show them how to change things around. Eventually, they can progress to building characters from the ground up, but it's easier to get them started by tweaking pregens to suit their preferences.