We all handle death, dying and grief in different ways. My dad died 3 yrs ago, from breast cancer. i am a nurse - I knew he was dying from the first diagnosis of metastatic disease. i had time to get used to it. My siblings didn't realize as quickly as me, and when suddenly it hit home, they were devastated. They both had time off work before and after he died, where I just got on with it.
What i am trying to say is, it is hard to not feel guilty for not being as openly grief stricken but you have a baby to care for, and you have to continue your life - your mum would have wanted you to. If you don't want to visit your mum, tell them - explain why though - perhaps it is that you don't feel it is her there anymore, and you would rather remember her in life.
I saw my dad once, just after he died. I wanted quiet time with him, to tell him I loved him, and my mum came in to check I was ok, so I never said it.
Dn't do things to please others (except maybe your Dad), but do explain why you feel the way you do, if you can, as it will help them understand.
Life does go on, and yu will grieve in your own way, as you are. Sometimes still, something happens, and I nealry pick the phne up to ring Dad. It breaks my heart.
Take care hope the fineral goes ok.