The fact that none of the three children in 1840 show up in 1850 suggests that all three were children of Wife-1 and that they may have gone to live with their grandparents or an aunt, perhaps because they didn't like their step-mother.  Either that or all three died, which is unlikely.

1a.  Anon.  1966.  Marriage Index:  Ohio, 1789-1850.  Liahona Research, Orem, UT (Broderbund CD-400):

Cupp, Samuel

Walters, Magdalena

8 Feb 1838

Fairfield Co.

1b.  LDS.  Family Search: Internet Genealogy Service:  IGI - International Genealogical Index (online at FamilySearch.org).

Lemon Valentine CUPP Birth: 1842, Fairfield, Ohio Father: Samuel CUPP; Mother: Mary Magdaline WALTERS Source: patron submission

2.  1840 Census Index and Digital Images (online at Ancestry.com; Image #21 of 24; extracted by Diana Gale Matthiesen):¤•

1840

OH

Fairfield Co.

Walnut Twp.

p. 352B

Ln. 31

Cupp Samuel

110 010 - 100 010

These data indicate:

No. & Sex	Age Class	Therefore Born	Individuals Inferred
1 male	4 or under	1835-1840	= Son B
1 male	5-9	1830-1835	= Son A
1 male	20-29	1810-1820	= Samuel (b. 1811/2)
1 female	4 or under	1835-1840	= Daughter A
1 female	20-29	1810-1820	= Magdalena (b. 1818/9)

There should be a female in the 1830-35 age class.  List is roughly alphabetized, so no neighborhood reconstruction is possible.

3.  1850 Census Index/Images (online at Ancestry.com; Image #48 of 51):  Walnut Twp., Dist. 41, Fairfield Co., OH, p. 219B, 1330/1330, enumerated 6 Sep 1850 (extracted by Diana Gale Matthiesen):¤•

Cupp Samuel	38	M	Farmer		O
"  Magdalene	31	F			"
"  Alaneda?	9	F			"
"  Lemuel	7	M			"
"  Jacob	5	M			"
"  Mary ?	4	F			"
"  William	2	M			"

Living next door to Samuel's father, Valentine CUPP, in one direction; and, in the other direction, living next to Peter LAMB (wife Mary WALTERS), who is next to Peter's brother, William LAMB, who is married to Samuel's sister, Catharine CUPP. 

4.  1860 Census Images (online at Ancestry.com; Image #4 of 54):  Pleasantville P.O., Walnut Twp., Fairfield Co., OH, p. 226B, PN 186, 1362/1362, enumerated 3 Aug 1860, official enumeration date 1 Jun 1860 (extracted by Diana Gale Matthiesen):¤•

Samuel Cupp	46	M		Farmer	8600	1500	Ohio
Magdalene "	44	F					Do
Almeda    "	20	F		College Student			Do
Lemon V   "	18	M		Farming			Do
Jacob W   "	16	M		Farming			Do
Mary E    "	14	F					Do
Wm M      "	12	M					Do
Edson B   "	10	M					Do
Theo P    "	8	M					Do
Delila L  "	6	F					Do
Charley H "	4	M					Do
Saml P    "	6/12	M					Do
Margaret Miller	15	F					Do

Living two households from Samuel's sister, Catharine (CUPP) LAMB. 

5.  Family Quest Archives:  Ohio 1870 Census Index.  Heritage Quest ACD-0014:  can't find.

6.  1880 United States Census and National Index (LDS Family History Resource File: CD-ROM Library):  not found, at least not in Ohio.

7.  WorldConnect / Ancestry World Trees (online at RootsWeb.com/Ancestry.com).