I don't think it's presumptuous at all, especially if it's a bulk sms (and it happened last time!). Personally I actually think it's rude to turn up on the doorstep straight after someone's had a baby WITHOUT calling to see if it's ok. I have NEVER been offended by someone saying "it's not a good time" or in the case of my SIL "I'm going to have a sleep now" (obviously a very gentle way of saying "please leave").

I hope no one is offended by a completely natural and normal wish to spend some time as a family before introducing your new bubby to the world. We certainly intend on having day 1 as only immediate family, and please call before visiting after that. But I have very practical family, they wont let me lift a finger

Good luck with your new arrival, I hope it all goes smoothly - and at least you know you're not alone with wanting to be alone, lol!