We are looking for the best way to get from CDG to the Villiers Metro area. It looks like the Air France bus to CDG Etoile would work ok, then a short Metro ride to our destination? We may not be flying Air France - don't know yet - but that shouldn't be a problem, right?
Yambu

The best way is by taxi -about 45€ to 50€.

For 8.70€, you can take the RER B to Gare du Nord, change to M2 direction Marechal de Lattre, and exit Villiers.

Anyone can use the Air France buses.

I think your idea of the AF bus and then a short metro ride to Villiers is pretty good.

The metro line that goes to Villiers (line 2) isn't that great a connection at Gare du Nord as it isn't really where the RER B or train station is. It runs north of the station on bd Rouchechouart, although I think there will be directions and you can walk there (underground) from the RER B stop, although it may be a couple blocks away. That would be to La Chappelle metro stop, that's the one that connects by tunnels. It's up to you.

If there are more than two of you, taxi is the same or less cost than the AF bus plus Metro, and would be easier and faster. If just two, it would cost a little more (about 10-15€) for the taxi than AF bus/metro option. Unless traveling solo, I have come to rely on using a taxi from CDG as it is just so much easier, especially after an overnight flight.

I don't see the Marechal de Lattre stop on my Metro map. Is it the same as Porte Dauphine?

Yes Marechal de Lattre de Tassigny is the same as Porte Dauphine. Do not board M2 in the direction of Nation.

Take the RER B to Gare du Nord.
Transfer to metro line 2 (access at the back of the RER train -- most people will be going towards the front, where the train station is as well as the other metro lines). Escalators (except for one light of stairs) will take you to the elevated La Chapelle metro station.
You want direction Porte Dauphine, and you will quickly arrive at the Villiers metro station.