Although... his mother's sister's husband's father was there - Mr Giles died in December 1851 at Council Bluffs on the banks of the River Missouri, on his way West, to Utah, at least 80% of the way there, but still 900+ miles to go.
Why did the Evans family go, given the risks - of starvation, drowning, hypothermia, infectious diseases, violent incidents, death in childbirth? Well they wanted a better life, in their version of the promised land. And they did not know that Mr Giles had died. Folks back home did not learn this for a year!
The good news is the Evans family started early. With Spring just beginning as they arrived in New Orleans there was a good chance they would make it upriver to Council Bluffs by June and the long walk to the Salt Lake valley in handcarts would be, should be, concluded before the onset of Autumn, and the chance of blizzards. One blizzard could wipe out a small party.
The problem is.... Well the problem is, the Evans family didn't make it to Utah. Something happened on the way.
Saints by Sea: the Kennebec passengers
Saints by Sea: what happened next to the Kennebec passengers
A voyage on a steamboat, the Saluda in 1852 going up-river
Aftermath: telling the steamboat story. What I cannot find are precise references to Native Americans in the area, nor of diseases such as cholera and yellow fever attacking folk. I cannot trace the parents making it to Salt Lake City. It is possible that William Evans, now just six months old and likely weaned, when the steamboat exploded, might have been adopted in Missouri, Iowa or just possibly by Native Americans....