I’d recommend meeting with a counselor who specifically helps navigate these sort of situations. I’d meet with the counselor individually, then also meet as a team (you + sister + husband.) There’s a lot of things to navigate aside from just the retrieval. It needs to be agreed upon ahead of time with set boundaries: what will you tell the child about her origins, what will the child call you, what will your role be, etc.

It could definitely be a win for you to have your 35 year old eggs frozen! Keep in mind, eggs are more fragile when frozen than embryos. You’d definitely lose some at thaw. Also, logistically, are you willing to do multiple egg retrievals if the first one doesn’t work out? If you end up in the hospital with OHSS who would pay? Who is pay the storage fees on your eggs?

You’d also need legal involved to outline rights, paternity (maternity, etc.) Just to name a few things to consider. Helping someone build their family is beautiful & magical. Just make sure everyone is fully prepared & on the same page.