I'm sorry but I don't think estrangements happen because young parents set boundaries. In cases like babybawns, imo, estrangement happens because the gps don't respect boundaries. A co won't necessarily be avoided if young parents give in and let the gps walk all over them. The more likely scenario, imo, is where parents reach a point of no return, as limit after limit is broken - and that's when they'll throw up their hands & decide to co the gps. I'm not saying that's true in all situations, but when gps are pushy like babybawn's ils, I think it is.
Babybawn, there's a saying: "Begin as you mean to continue." Imo, that's what you need to do. If you intend to continue treating dh's side of the family better than your own, then, by all means, start now. If you plan to continue giving into your ils demands and letting them step on your boundaries - or not bothering to set boundaries at all - because why bother? They'll just ignore them anyway - then go ahead and let them visit a couple of times or hey, maybe as much as they want. If you're ok with disrespecting your own dh's wishes in order to placate your ils, then, he might as well know that right now.
But if you would like for you and dh to be able to make your own decisions about your own child, etc, if you would like to be able to set boundaries and have them respected, then you need to be firm now. Could you give in this time and set better limits in the future? I guess, but it will be harder. But only you can decide what pattern you wish to establish. I hope you make the best choice for you and yours.