Spousal sponsorship with her dependent

[Dejavu2020]

I'm sponsoring my spouse with her dependent child(6years) but she never married. I need some advise on how to sponsor both of them and what documents I might need especially for the child to come to canada. I have documents to proof my support for 2 years. The child has her mums surname because the dad has never been involved in their life since birth. Can I use the surname to prepare the child's documents even though the dad as agreed to give consents for taking the kid to canada and changing of names if necessary. Thanks