This is a big question for us, too! My mom is complicated, so she isn't invited . . . at all. My MIL is wonderful, and she lives 3,000 miles away and is planning to come and stay for a few weeks. It seems a little daunting because I want to have private family time with my husband and our baby (this is our first), but I will be glad for the help because my husband doesn't even know how to hardboil eggs, and my MIL is an INCREDIBLE cook. I felt kind of awkward at first because it seemed like she wanted to be present at the birth, but then when I talked to my midwife, she said, "since you'll be delivering in my house, I only really allow for your husband to be present because my family needs their space, too!" so that made it an easy decision!
The only real "question" I guess we have is when she should arrive. She wants to be here before baby, which is fine by me because I need all the help I can get preparing (I intend to do a lot of canning and have a spotless house), but you can't predict when a baby will arrive- especially the first one! She also has a limited time frame and will need to buy plane tickets in advance.
Also, I know my MIL will understand we need some amount of privacy because the first time I met her I stayed at her house with my husband for over a month (we weren't married yet) and she let us stay in a room by ourselves and didn't ever come in unless there was a lot of advance warning! So I trust her.