"I would like goat meat and rice please."
Translation:Ninaomba nyama ya mbuzi na wali tafadhali.
Yes, ningependa wali literally means "I would like rice." Naomba wali literally means, "I request rice." Ninaomba wali means (iirc) "I am requesting rice" as in, at this very moment, the activity I'm engaged in is the activity of asking for rice.
In my experience, both "Ningependa wali" and "Naomba wali" are courteous ways of asking for rice, although the latter is more common. If you wanted to be rude, I suppose you could say something like "Leta wali tafadhali."
Politeness in Kiswahili is expressed through grammar, rather than tagging sentences with a "polite" word, as we do in English with "please." The Kiswahili word "tafadhali" means "please" in the sense of, "Would you kids PLEASE get off my lawn already!" It expresses exasperation, or emphasis, rather than courtesy.