Everyone is so different on this and I think it really comes down to what your relationship is like with your mum.
My mum and I are extremely close and I couldn't imagine NOT having her around to help when my kids first came home.
I was such a hormonal mess both times that DH was grateful for her to be here as well because she's the only person that can sort me out when I'm like that LOL.

When DD was born we arranged that I would come home on the Sunday and mum would give us a few days to settle down and she was coming on Thursday.
I got home Sunday afternoon and first thing Monday morning I was on the phone bawling and telling her to get here NOW. She lives a few hours away and she arrived that afternoon.
When I had DS she was there from the day I got home - which was good because I had an unexpected caesar so we really needed the help with Emily.
Just do what feels right to you, and leave your options open.