I am assuming that you are descended from Marcellin, since he was the only child you listed.I looked in Father Hebert's Southwest LA Records, Volume 2 (1810-1830).I found two Marcellins -- only one of them has a father named Joseph (who married Celeste Dugas) but his parents were not Jean Dugas and Marguerite Dupuis.There seems to have been a second Joseph (son of Jean and Marguerite) who marrie Anne Celanie Breaux.
p 287 DUGAS, Marcellin (son of Joseph and Celeste Dugas) m. 7 April 1828 Melanie Boudrou (Laf. Ch v1 # 83)
p 286 Dugas, Joseph pere m. Celeste Dugat d, 15 Aug 1830 at age 61 years (Laf Ch v2 p 96)
Dugas, Joseph dit Foraz m. Celeste Dugas Succ. Dated 22 Dec 1830 (Laf. Ct Hse # 196)
DUGAS, Joseph (son of Jean and Marguerite Dupuy) m. 10 Feb 1812 Marie Celanie Brau of St. Jacque (SM Ch v5 # 248) --I don't think this could be the same Joseph as the father of Marcellin, not when Father Hebert lists a different set of parents and when Joseph's death record lists his wife as Celeste Dugas.
DUGAS, Jean (Joseph and Celeste Dugas) b 8 Aug 1812 (SM CH v6 # 1426)
From Volume 1 (pre-1810). p 191 DUGAS, Marcellin (son of Joseph and Celeste Dugas) b 2 Oct 1804 (SM Ch v6 #267)
This is the only other Marcellin.His father is Celeste Dugas's brother: DUGAS, Marcellin (Pierre of La Grande Prairie and Marie Gauthereau) b 8 May 1807) SM Ch v6 # 428)
And it had this other information about Joseph Dugas:
DUGAS, CELESTE (daughter of Jean and Anastasie Dupuis) m 2 Aug 1794 Joseph Duga (son of Charles and Marguerite Grange) (SM Ch v4 # 99)
DUGAS, Celestine (Joseph of St. Malo, France and Celestine Duga of SM) b 27 July 1809 (SM Ch v7 # 284)
DUGAS, Joseph (Joseph of St. Malo and Celeste Duga of Atakapas) baptized 24 Mar 1799 at age 6 months (SM Ch v5 # 117)
DUGAS, Marie Aspasie (Joseph and Celeste Dugas) b 13 Mar 1796 (SM Ch v4 # 792)
DUGAS, Marie Aspasie (Joseph and Celeste Duga) d 11 Sep 1798 at age 2 1/2 years (SM Ch v4 # 159)
DUGAS, Marie (--- of France and ---Dugas of SM) b 8 --- 1802 (SM Ch v6 #34)
DUGAS, Marguerite Silesie (Joseph of St. Malo, France and Celeste Duga) b 3 Feb 1807 (SM Ch v7 # 143)
SM Ch = St. Martin of Tours Church PO Box 71 St. Martinville, LA 70582 (records dating from 1756)
LAF ch = St. John Cathedral PO Box 2386 Lafeyette, LA 70501 (records dating from 1821)
I just did a quick spot check of these two volumes (I don't have access to the others), and I think I got most of the children.I may have missed one or two.
Let me know if there is anything else I can do for you.