Training Trixie as an assistance dog

Joseph is a young boy (aged 7 years old) who was born with Schizencephaly. Schizencephaly is a rare condition that occurs 1 in a 100 000 children. It has affected Joseph in that he has suffered seizures from the age of 12 months, affecting his development. Joseph is in a wheelchair and needs full time care.
We are raising money to buy a companion dog for Joseph. The dog that we are looking at is a labradoodle that has the temperament and personality suitable for Joseph's needs.