There are also a number of restaurants in Brookline on Harvard Street- Butcherie, Rubins Kosher Delicatessen, Rami;s Falafel and Taam China which also has a place in Newton
My personal favorite is Taam's excellent kosher chinese - you can also check out http://shamash.org/kosher/ for reviews or also post to the kosher board of Chowhound -
428 Harvard St, Brookline, MA 02446
Taam China Restaurant
423 Harvard St, Brookline, MA 02446
Taam China Restaurant II
108 Oak St, Newton Upper Falls, MA 02464
Rubin's Kosher Deli
500 Harvard St, Brookline, MA 02446
Rami's Food Products
324 Harvard St, Brookline, MA 02446
The Butcherie is not a restaurant, it's a kosher grocery - useful if your guest wants to pick up some food to eat at home. They also have a good selection of kosher wines, Israeli and otherwise. The other three you mention are all good options but quite different in atmosphere.
Rami's is a falafel joint, emphasis on joint. Great food though. Rubin's is a classic fleischig Jewish deli with everything from chicken soup to corned beef. Not the best corned beef in town (that honor goes to Michael's Deli) but certainly the best glatt kosher.
Ta'am China is the most white tablecloth of the bunch, and also has a full liquor license, so might be a better choice for a nice dinner out rather than lunch. The food quality does not remotely approach the real Chinatown gems, but is better than you'd expect for kosher Chinese.