OP, the best adventure game for a beginner is without question Curse of Monkey Island (MI3). It has everything:
-One of the best interface systems
-THE best graphics in any adventure
-Excellent characters, writing, voice acting and songwriting (!)
-Good to great puzzles
-Cartoonish setting with a lot of heart, fun for the whole family like a good Disney cartoon
The second best choice I would say is Leisure Suit Larry 7: Love For Sail. It was Sierra’s best adventure overall. It has a lot of the things that make MI3 great, in a ribald but not really pornographic setting. LSL7 also has the best adventure interface ever, which ingeniously combines the ease of use of that of MI3 with the power of a text parser. It’s a real tragedy that after these outstanding games were released, the genre promptly shat itself in 3D and then collapsed. Adventure games could have easily survived if they just churned out dozens of great games in this Disney cartoon style with the mature point and click interface.
Also, these games are some of the funniest ever, funny in a way that is all but forgotten today. True gems from a lost era.
After that you could move on to Grim Fandango, Gabriel Knight, QFG, SQ5... great games but somehow flawed that I wouldn’t recommend them to a complete newb.
But Grim Fandango takes it to a whole new degree. The first area of the game involves one bottomless dialogue pit after another, sufficient that my kids just quit.
Your kids are dumb. Shame on you for spawning such incomprehending little Philistines.