Is 50/50 the starting point whatever the age of the kids? Mine are age 2 and 4. I gave up work to be at home with them and have been the primary carer, though they also are used to seeing their Dad and obvs it would be important for them to continue spending plenty of time with him.
We haven't talked about separating yet, but I am thinking about it. The young age of DC's is the biggest stumbling block for me. Not that I'm sure it gets easier when they older, but I do think separation can be harder for very young children.