I have to say I'm not sure what your description refers to. Yoshinkan doesn't do a lot of stomping.
In general, outside of a dojo I would almost never do nikkajo right off the bat. I'd do Ikkajo first, then while uke is bent over and off balance, move to nikkajo (you mentioned doing it from a shomen strike). Off of a grab I might go straight to nikkajo, especially if it is a shoulder grab...but usually only after hitting the guy in the nose first.