To find descendants, it's important to follow each person to their death. Then you can order a copy of their obituary and look up their survivors in zabasearch.com or spokeo.com.
I did find Manuel Souza and family in 1910 in Koloa, Kauai, Hawaii Territory.
Manuel M. Souza, all family members Portugese, b. Portugal, 31, immigrated 1881, alien, teamster sugar plantation.
Mary, wife, b. Hi, 24, had given birth to five children but only four alive in 1910.
Annie, b. HI, 6.
Antone, b. HI, 4.
Manuel, b. HI, 3.
Isabel, b. HI, 9/12ths.
I didn't find any additional information about this family. Hawaii restricts access to vital records until 75 years after the event. The oldest records are on file at Hawaii Archives, hawaii.gov/dags/archives.
The Hawaiian Sugar Planters' Association Archives has records from sugar plantations on most islands. Go to www2.hawaii.edu/~speccoll/hawaiihspa.html.
In 1920 Isabela Freitas and family were living in Lihue, Kauai, Hawaii Territory.
All were Portugese.
Isabela Freitas, head, b. HI, 30, widow, no occ.
Frank Freitas Jr., b. HI, 9.
Joseph, b. HI, 8.
Daisy, b. HI, 5.
Isabela, b. HI 4 4/12ths.
Anna Souza, neice, b. HI, 15.
Elizabeth Souza, neice, b. HI, 10.
Olivia Souza, neice, b. HI, 7.
Virginia Souza, neice, b. HI, 5.
Henry Souza, nephew, b. HI 3 1/12th.
The Freitas family in 1930 was living in Koloa, Kauai, Hawaii Territory.
All are listed as Portugese.
Frank Freitas, b. HI, 19, married, sailor merchant vessel.
Joseph, b. HI, 18, brother, single, laborer, pineapple plantation.
Olivia, sister, married, 17.
Daisy, sister, single, 15.
Elizabeth, b. HI, 14.
Ruth Marie, niece, b. HI, 1 2/12th.
Gilbert, nephew, b. HI, 1/12.
The 1940 Census for Hawaii is 40 percent indexed. You can check on the status at familysearch.org and then look up these folks on that Census.
I also found My Family Tree, trees.ancestry.com/tree/16693909/person/608994894 which contains your Silva, Freitas and Souza families. Most larger libraries provide free access to Ancestry. Thought you'd want to get in touch with the owner of the tree.
Their is an obituary volunteer for the entire state of Hawaii at freepages.genealogy.rootsweb.ancestry.com/~obitl/volhi.html .
I'm not related but Successful Searching!