The family, from Loganlea, Queensland, were heading to a reunion with Williams' New Zealand family. They had intended to be here for two weeks.
A GofundMe page set up for Williams and her daughter had reached $24,213 by 8am today.
The grieving family, in a statement on the Waikato District Health Board website, thanked well-wishers.
"The families are finding this a huge comfort at this very sad time."
Today, a health board spokeswoman said Williams and Tessa were in stable conditions.
"Police's thoughts are with all those involved with this tragic incident, including family, friends and emergency services who were at the scene," police said.