Vent-I can't check your mail for you! (Long story)

Our OA requires that my son's bio mother contact me by mail by the 15th of the month prior to the scheduled visit month to provide me with three possible dates to choose from. I am required to respond by mail. I am also required to send an update and current photo every year in December. One of the lawyers involved in the case advised me to always send all my communication with her by Certified Mail so that I have proof of delivery, if there is ever a question about it.So, this month I received her letter regarding the visit on the 17th. It was postmarked the 15th though, so no big deal. In her letter she also reminded me that it is December and she hasn't received her update yet. She also asked whether I preferred that she send a gift or gift card for my son for Christmas.Well, I had the update letter already written and was just waiting for some pictures I had professionally printed to arrive. I always send several photos from different times of the year, more than the required single current photo. As soon as they arrived I put them in the envelope, added a few lines letting her know which visit date worked for us and sent it by Certified Mail on Dec. 19. I also told her, not for the first time, that a gift card was best, especially since my son's wish list was already pretty well covered. I refrained from mentioning that even though she has asked me about gifts/gift cards for Christmas or birthdays over the past couple of years she has only followed through one time.Fast forward to today. I received another letter from her reminding me that it was December and she still has not received her update letter or my choice for the date for a visit! Using my Certified Mail receipt I tracked the letter and it was delivered on December 20th and a notice was left for her.At this point we are way past the deadline for her to be able to arrange the visit, especially since the Visitation Center we use is very strict about following the letter of these agreements. I just printed out another letter for her stating this fact and telling her that the original letter has been delivered, but she has to actually go in and claim it. If she doesn't claim it within 15 days it will be automatically returned to me. I let her know that if it does come back I will resend it one more time. This is also not the first time this has happened. We went through a similar thing over the summer, and there was no visit because she couldn't or wouldn't claim her Certified Mail. Now I'm wondering if I am just being too rigid about it and maybe I should just take the chance of sending updates and responses via regular mail, in spite of the lawyer's advice. I really don't want to withhold the information from her, but at the same time, I do want to stick with some boundaries. It just feels like she should be required to at least manage this one fairly simple responsibility she has in order to arrange these visits. All she has to do is claim the mail and call the Visitation Center to confirm the date. That's it! Oh, and she does have to pay for it. My son (10) knows what months visits are supposed to happen and that his bio mother is responsible for arranging them. So far, he has been very neutral about the whole thing. If they happen, fine. If not fine. I do worry that some day he is going to wonder why she couldn't follow through and may feel like she didn't care enough about him to do it. Sometimes it feels like she is doing just enough to make it look like she is trying, but then she allows the dates to slip by or something happens to prevent her from getting her mail or being able to contact the Visitation Staff.Am I being totally unreasonable? Or should I stay firm and expect her to be able to manage this much?