My question involves a child custody case from the State of: Nevada

I am writing for my husband. His ex has custody of their 2.5 (3 y/o next month) year old daughter, they had been trying to work out a 50/50 custody agreement.. or so he thought... but in the end she said that she would consult her attorney and that she didn't want to agree to anything without court involvement.

Well tonight on the phone his daughter was saying that she wanted to come to daddy's house and play with sister (mine and my husband's daughter). Then she got quiet and almost sounded sad and said "but mommy says I don't want to go to daddy's house".
This is not the first time she has said something like this and he wants to know if it would be legal to record his and his daughters conversations.

There are a couple reasons why he wonders this -
1) His ex has physical custody. So being as in Nevada both people have to consent to the conversation could he consent for her? They do have joint legal.
2) sometimes his ex says something in the background. Again if she is talking in the background or if she has the phone on speaker phone how does this work with recording?

Thank you