Jory, I think your wife needs you, she needs some of your time to be with her alone. cheer her up, make her laugh and tell her that there is nothing more important in this world but to be with her and your children.
As a mother and a wife, there is nothing i want from my husband but to hear and see that he cares about me..spend some of his time with me and to play with the kids. I'm so grateful for my husband and so I encourage u to do the same to your wife.
Give a try and never show that you so tired....she will understand later on but for a start...cheer her up.