It might be wise to get index thumb shifters if the bike is for someone who doesn't want to fine tune with a friction shifter. Friction can be fun and I had friction shifters on my road bike until earlier this year, but there is a reason why Suntour went out of business and it wasn't because of their quality.

Also you don't need to run all 3 chainrings in the front. Depending on the terrain, you can probably just use the middle/big (small/middle if you ride in hills). It makes for real easy front shifting... one way one chainring, the other way the other chainring. Just turn the limit screw on the front derailleur to stop the derailleur from moving the chain into the small chainring.

John