YANBU!
I'm pregnant for the second time now, and boy have I learned from the first experience! My mum arrived from Cornwall (I live in Kent) while I was in labour, and hung around in the delivery room until my son was born (sending my Dad home just half an hour before he appeared. My dad had taken me to appointments throughout, and drove DP and I to the hospital, so that was a real blow for me not to see him soon after. She then proceeded to hand around in the hospital with my brother and sister (my brother, bless him, was 16 at the time and built like a house. He has ASD, so lovely, but kinda awkwardly in the way.)
My Dad drove us home from the hospital after a few days of crowded misery in the ward, and we had a tiring but wonderful night alone with DS, which was terrifying but hugely important to our confidence. If you have any concerns that parents or in-laws might take over or sit there telling you what to do, say no. You have to work things out for yourself. I was so glad we had no one staying at night, as the first few days seemed to be full of people sitting everywhere in our small house, cooing over and holding MY baby, while I felt lost, in pain, and cranky. Never again.
You need to have set visiting times. If you feel you can handle more than you'd thought once the bab'y there, then fine, have people stay longer, but that's a lot easier to arrange than kicking people out when you promised them a whole day! And make sure the balance is there too - my mum totally hogged DS when my in-laws arrived, with the reasoning that she wouldn't see him for months. I don't think they even really got to hold him the first time they saw him, and my MIL has never really forgiven my mum. Nor has DP, though obviously his bigger problem is that she ruined the birth for him.
My dad, on the other hand, wonderful. Came round for short periods of time, did bits of washing up, asked DP how he was coping with all the changes (he was the only one who asked that, too) and generally was there when we wanted him, but away when we didn't. If you think that this is how a relative will behave, then you don't need to point it out to them. They'll act decently. But if you're concerned, it's probably with good reason. Set the boundaries now, because in the chaos after delivery you could well get swept along like I did.