ok heres my opinion. please don't flame me, its just an opinion
if I were sil and you were trying to do this your way, like that with regard to MY decision to put my child up for adoption, I would be livid. There may be reasons she does not want to have an open adoption, & it is her reasons and it really isn't any of your business if she doesn't want it to be your business. I am sure adoption is hard enough for her, not having you doing this. I obviously don't know your family and the whole senario by your one post but giving the facts you gave I would be pissed at you.
sorry..
side note: keep in mind my experience with adoption is limitd so I may be way off this is just my feeling. but My brother adopted his first child and hadn't decided when to tell his daughter yet (she was 3 (this was early eighties),his sil stepped in and told her for him! because she thought she needed to know
people need to stay out of peoples business unless asked to be in said business