Caitlin or Kate. Katelin is hideous.
I prefer Katherine with the nn Kate (that is my DD's name), but if you like Kate I think it is find as a stand alone name.
Kate Elizabeth is pretty, but I'll warn you that literally every Kate I know who is "just Kate" has the middle name Elizabeth. I know three Kate Elizabeths.
I love Lauren and Jonathan. It is a shame you dislike Katherine so much because it does sound good as a sibset. Have you considered Kathleen? I have a friend who goes by Kate but her full name is Kathleen.