Hi Danielle.
I was in the same boat as you, worried sick what will happen to my daughter when I die. So I went to a solicitor and made a will. Her Dad left us when she was 3 months old, I wasn't married to him but his name is on the birth certificate. She is 11 now and he has never tried to get in contact with her and I have never contacted him.
I stated in my Will three Guardians for her if I pass away before she is 18. I know you mention your Mum, and I have put my Mum as one too, but she is no spring chicken and if she dies before me , I know that I have a back up plan with the other two Guardians.
It's a relief when things are set in stone. (As good as anyway) Do it sooner rather than later.
x