Ms Brown said the funeral, on 13 January, would be a time to “celebrate” William’s life.
“We want to remember what a wonderful, beautiful boy he was,” she said.
Paying tribute to him, she added: “We had seven wonderful years.
“It’s been a privilege and an honour to have William as my son.
“He is going to be greatly missed, but the memories will shine through forever.”
A 49-year-old man arrested after the crash has been bailed until March pending further inquiries, according to Kent Police.