The Regnier is question is the one who became duc de Massa, as I said and a quick check with Reverend's "Les Familles Titres et Anoblies au XIX Siecle" identifies him as Claude-Ambroise.
Looking up Kellerman in the same work I find that Kellerman Jr is described as 'comte, puis duc de Valmy' . You probably aren't finding him because it was a courtesy title and not an award but I have seen the title used in Napoleon's Correspondance.
Looking up Lannes (as an example) it is a bit confusing since his heir is only listed as 'duc de Montebello' but there seem to have been three courtesy titles awarded : Alfred is 'comte Lannes de Montebello et de l'Empire (lettres-patentes du 9 mars 1810)' and Jean-Ernest and Gustave-Olivier are both, 'baron Lannes de Montebello et de l'Empire (lettres-patentes du 9 mars 1810). All of them under 10 years old at the time. I think that the 1810 date may have been when the courtesy titles came in, by which time the heir had already got the main titles and therefore his next brother was his heir.
Reverend's work can be a bit confusing and occasionally gets dates wrong but it is still invaluable for sorting out the families and titles. If you can't get a copy, I have all three volumes and will look up anything that might help.