"Ustedes" is plural You, not They. They is "Ellos/Ellas", depending on the gender :) and Ellos son-They are Nosotros somos-We are Ustedes son-You are
"vosotros" is plural You as well, but it's used only in Spain and Equatorial Guinea
Don't forget you can have Nosotros estamos... (we are) and Ellos Estan...(they are), because there is more than one verb for To Be. You are conjugating Ser, but lets not forget Estar. Nosotros estamos en el restaurante. We are in the restaurant. Location and Condition Now (to name a couple) uses Estar and not Ser. I am not sure at your level if youve encountered Estar vs. Ser yet, but its a big topic when learning spanish, so this is a heads up.
heres the first of 4 tutorials on the subject of Ser vs. Estar