Jonathan D Heywood
I hope this is the right info and that we found the right J.D. Heywood. This info is linked to G A Heywood so it seems the most likely. It looks like he stuck around and didn't trek to Utah.
Gardner Allen Heywood
"When the Mormons moved to Salt Lake, the Heywood family was all that was left in the place [Springville]." http://trees.ancestry.com/tree/15417518/person/300416015/media/2?pgnum=1&pg=0&pgpl=pid%7cpgNum
She either died between the 1850 and 1856 census or was married in that time period. Since she was so terribly young I would guess that she died.
she most likely died in Nauvoo, Hancock, Illinois but there are no sources that specifically indicate this.
Samuel Ely Williams
In 1850 Samuel journeyed with the David Evans Company to the Salt Lake Valley.
Mary Williams Galloway
In 1850 Mary journeyed with the David Evans Company to the Salt Lake Valley.
Robert G. Williams
"At the time I was the worst the day before Mr. Robart G. Williams a brother of Phinious Pettegrews Wife was lying in the wagon nere ours who had the Coleria and died[.]" - Trail exerpt sourced in sources.