Then it shouldn’t be “Taobī”. “Muñi taobī” means “The mothers and the boys”. The sentence should be “Muñi taobi rijis”. As it is it means “The mothers and the boys are praising”.
'Taobi' is nominative, accusative is indeed 'taobī'. Both interpretations can be made and only in speech the ambiguity would disappear (we'd say "TAObii" if its the object and "taoBII" if its "moms and boys", both subjects).