Well, having been through the DE and also adoption thing I might have a little different perspective? I say that bi-yearly updates is very little to ask. In fact in comparison to what you are getting, the cost of a picture twice a year is less than minimal.
In most adoption cases now the bmom can ask for and gets exactly how much contact she needs/wants. In most cases their interest wains after a bit of time, but still in the world of morals and ethics, they have the right. In the world of law, the adoptive parents do not have to comply once the adoption is final. It would be the same for you. But, would you really want to do that? It's not like they are asking for visitation every other weekend and 2 weeks in the summer. YOU are the parents, they just want to see how the embab(ies) they love are doing.
I am not saying the whole thought of this is not scary. I know the fear. And it is understandable. You are new to this whole world of non-DNA carrying children. It is all pretty new and frightening in the beginning.
Once you have that baby and you realize how much she is yours, then the fear lessens. Then the reality that she is only YOUR baby. And then you can't WAIT to share her with everyone you know and that becomes your modus operandi, instead of fear.
In my case, my egg donor was anonymous. And it makes me sad. I have wished, many, many times I could share with her donor how beautiful her egg has become. How she's bright and wonderful and the love of our lives. I wish so much I could share with her just how much her gift has and does mean to us. I would love to see her and compare how Avery looks to how she looks I often wonder if Avery has her DNA mother's eye color or does she have her hands, etc. We will never know and we were not given the gift to be able to share our miracle with the people that would appreciate it as much as us.
Be happy you have people that want to be able to love from afar. It means your baby will have the fantastic genes of caring, wonderful, giving people. How could that be wrong?
Feel free to disagree with me. Feel free to PM me and chat about all of this. It's a big thing, this. You are a pioneer. And sometimes you feel like you are in this alone, but you not. I am here. And there are other people I really admire here that have gone the route you are choosing to go. Feel free to pick our brains. I think we'd all love to be able to give back some of the joy we've been given through the world of donor eggs, donor sperm and donor embryos.
Hang in. This won't be the last time you panic about something.

But whether your child is 100% your child is not one you have to actually worry about. Trust me on this.

~m
One more thing... you can never have too many people that love your child.