So I'm inclined to wonder if this is a money move. If you have hands on/face time with the kids 12 days out of 14 if it's broken down into hours there's a chance you could demand child support. Some places it's all about the over nights, some places it's actual hours with the kids so I'm not 100% on that but I'm always kind of expecting the worst of the parent who has less face time with kids. And it's something you should check in with your lawyer about.
But, and this is a big but, if the order is 50/50 and it actually means 50/50 you have to understand this isn't her taking away the kids from you, but actually holding up her end. I know it doesn't make the blow any softer, but it's what you're working with. And if that's the truth here it's a waste of your money to get your lawyer or the courts involved. I'm sorry.
There's a very fine line in co-parenting where you have to ask yourself if you're co-parenting well and sharing responsibility or you're using/being used/relying too much on your ex(and vice versa) to do things you really need to figure out yourself.
You're a hands on dad. Your littles are still really little. I totally understand why you feel like they are being snatched from you. This could've been handled better than kind of bomb dropping it in an email, but I have to agree with Maika sort of. I'd reverse the question. Not "is this better for the kids?" but "is this harmful to the kids in any way?" Because that answer is clear. It's either a yes or a no, and if her parents are stable and sane people you know the answer to this.
I know when this is all still fresh every step of the way feels like another step on broken glass, but you have to understand it's really important for her to be responsible for the child care on her weeks. Just like you should be responsible for yours. You two should only rely on each other in emergencies. You have two separate household, and two separate lives now. Both of your lives should be minimal contact with each other outside of trading the kids off, or kids updates/emergencies. Healthy happy co-parenting relies heavily on the clear separation of your lives in the early years. Eventually it can lead into trading days, and more lax versions of your court order, and if you're really lucky someday co-parenting with bonus parents in a healthy, mostly happy, integrated way. But most couples aren't lucky enough to make it to that top tier. And until you guys have done this co-parenting thing post divorce for a few years it's best to parallel parent.
Problems happen in the future if the laissez-faire custody happens. There will come a day when she dumps the kids off unexpectedly when you have plans since it's not your week. And I'm not insinuating that your children are a burden in any way, however, when you sink into your life with 50/50 most people arrange their lives based on the week with their kids and their week without. The potential you have here is you planning a week long vacation and her saying she doesn't have a sitter and has to work and now you're losing money and time to yourself. It leaves room for her to do something like that out of spite, or simply because she knows no matter what you're just going to take the kids. And she'll walk right through boundaries if she knows they're permeable. It could even end up where it's expected that you pick up the slack when she can't and then when you bring up the fact that it's not your week and that she does that, she can turn it around and make it a you don't want to spend time with your own children thing. There is a lot of messy messy things that come with not establishing boundaries and rules early that will put the kids directly in the middle of your D for the foreseeable future. That's not good for you and that's really not good for them.