Okay "chakula cha asubuhi" is a literal translation. For more accuracy you'd be better off saying "kiamsha kinywa" (which literally translates to "that which wakes up the mouth")
For supper, rather than saying "chakula cha jioni", say "chajio/kilalio" (which literally translates to "what I'm sleeping on") #doesn't make much sense, I know. Any way that comes easiest though is fine.
Because chakula is ki-vi noun group. So there must be "cha". In the plural (vyakula) it will be "vyakula vya..."