I don't divide my time for my parents or inlaws. Im living & working with my inlaws. So whenever i get time away without them, i am enjoying it. As for my parents, they are always busy working and enjoying their time. So probably once a month we arrange for a meal together. Thats all.
I don't divide. frankly the only way I could suggest is prolly to have a weekend meal and that's it. what matters most is your spouse and your kids. basically your family. everything else is secondary and parents should understand and respect that.