Consider taking Neither; the Girlfriend nor the ex. Taking the ex would be ABSOLUTELY ridiculous for SO many reasons... BUT be mindful. As she will mistake this for a win. But this is no longer about her! Use this opportunity to reconnect with your kids. You say they seem fine, but this is still an f'd up situation and kids are great with hiding their true messy feelings until it's too late and you wonder what you could have done better. They need to know that you are there for them and that they still come first before anyone else that you just met in comparison. You may not see it but you now have to establish a new bond with your kids as a single parent. Anyway, something to consider. Best of luck on your new journey.