My husband won a custody case for his son, and in doing so, the judge ordered visitation to the mom for every other weekend and shared holidays. He did not include anything about summer or school holidays. After the hearing, our lawyer wrote up an agreement for both to sign and send back to her, which basically granted the mother two weeks of summer vacation in July and two weeks in August, plus Thanksgiving this year, most of Christmas break (because it's just the way it fell this year with the dates the kids get out of school, she'd get him the afternoon of Xmas day), and spring break. She was supposed to sign the documents and return them, and advised my husband that she had, however, he just learned from his lawyer that she never received the written agreement signed by the mother.
Is there a way for the lawyer to void out the agreement since it has been almost 3 months since it was sent the mother, so they will be required to just go by the court order that was issued by the judge? Or will the mother be able to sign the documents at any time she pleases and send it back and it be considered legit?

I'm asking because the mother is extremely vulgar and the hygiene in their household is disgusting, we get my stepson reaking of stale smoke and dirty animal every time we pick him up, and we feel now that it would be in his best interest to not have as much time as was written in the agreement that was not signed.

State is Virginia. Sorry.