OPP means one penis policy, by the way. If you don't WANT to date other men, this is fine. If you have decided you DO want to date other men, you just do it. Your hypocritical husband can deal with it.
It's difficult to have 2 polyamorous parents when children are young and need care around the clock. But it's not fair that you're always home with the kids while he's out dating. When does he stay home with the kids so you can go out and do whatever you want to do? If you really want to date other men, that's your choice. Modern polyamory is feminist-based. The whole point of it is that women can love, date, and have sex with more than one man, if she wants. Let's face it, a man having more than one female sexual partner has always been more acceptable than a woman having more than one man. This is a patriarchal concept.
We live in a patriarchy. Our world is pretty much run by (white straight) men. Women are making inroads, but we have a long way to go. One thing we can do is, when we practice polyamory, make sure each partner, no matter their own gender, can date the gender of their choice. And this goes for bisexual women too. Many men would rather their wives date other women than other men. Their idea of FF sex is "hot." Their idea of their wife with another guy is, "He's encroaching on my territory, my possession, my woman." Men think they own women because, until very recently, they legally did own their wives!!
So. Get woke. Stop acting like a possession. Until about 100 years ago, a woman was owned by her father. Then she went directly to being owned by her husband. If her husband died, she was again owned by her father, or even by her brother or her own son, depending on who was alive. 100 years ago, women couldn't vote.
We have a say now, so don't be silent.
One more thing: If you're lonely when your husband is out on dates, you can spend time with friends and (adult) family. It doesn't have to mean you need another man. But if you really do feel like you'd enjoy dating other men, by all means, do it.
Your husband should be watching the kids just as often as you do, so you can go out and do whatever you want, even if it's just to the gym, or shopping, or pursuing any other hobby or interest. (Moms can forget they have interests... We spend so much time meeting others' needs.) It could be going on a date with a prospective romantic partner, but it could be anything else that you enjoy. The point is, you both get equal time to go enjoy yourselves.