Hi OP, I haven't been in your position as no children but my partner is unable to be available for me when I need extra help due to both of us with severe illness which affects absolutely everything.
However, when home you will be recovering from what is major surgery and you need to work out what help you need, what level you would be comfortable with, practical, emotional, baby and otherwise
Can I suggest something like the Jointly app = which can be downloaded to phone, tablet, laptop etc - it will give you a Circle of Care - the care, in this case, is your baby. It does have a one off cost of 2.99 but works very well (i use it personally for all care related things outside my care package)
Let him visit you when you are home at planned times, while he is there so say X hours in morning for example, there is a list of tasks he has to complete while he is there seeing the baby, he doesnt just get to sit and coo at the baby,
As in this example you have the other 20 hours and yes things still need to happen, baby needs to be fed, washed, changed, as do you.
You need good food as recovering from an operation,
The house still needs cleaning, washing up, bins, washing on/off, drying sorted and put away, shopping, other errands. This still needs to happen.
He doesnt get to come for just the cute parts if he wants to step up longer term he gets the whole shebang,
While he is there, he gets to handle crying, you put in earplugs and try and sleep, have a shower, something for you as every single ounce of your being is shattered, sore and bruised after giving birth.
You may be planning to breastfeed, for the planned visits, I would suggest if possible trying to express before he comes so that he can feed the baby while he is there. To give the teat of a bottle thru a hole cut in a tee shirt on the chest over his man boobs. It will give as near of an male breastfeed as possible.
If both of you decide to rebuild the relationship thats something to look at down the line,
He left you at 26 weeks, (maybe was terrified at the idea of being a father?) but you were well into pregnancy and experiencing all the side effects and getting the brunt of it. So not cool from him at all.
As for his mother, if you think it would be good for both her and the baby to see each other, its on your terms. A short visit to cuddle the baby on X day between X and Y time. A visit to help with practical side of things on X day, babies arent just for cuddles.
She can also cook you some home made meals - give her practical stuff to do and short planned visits with baby. Practical help will let you recover from major surgery. It will let her feel useful and she gets to see baby but you know you only have to endure her till X time and when your ex or MIL is there , not at the same time visiting (stuff of nightmares)
Your baby (you are the one carrying), ex has less standing at this point in my eyes as walked away at 26 weeks so your house, baby and make a list of rules if need be as then they can relaxed over the coming months and years. Start as you mean to go on.
Good luck with the CS and Congrats on your baby