You can name them Elizabeth and Consolacion and still have their nicknames Tami and Cami just because nicknames can have no explanations whatsoever.
If you're into themes then Tamera and Olive (Tami and Ollie), both palm trees, or Polaroid and Kodak (Polly and Cody), photography. :)
Now, if you really insist on it, Tamera and Kamara. Still the same thing but more archaic. Just beware. The names you give to your kids has a way of sticking, somehow. As a teacher, I've known a bunch of John Paul's, all named after the pope. They were all quite the opposite of their namesake. I had a student named Einstein who was always first from the bottom in ranking. I named my first son Vernon since it had a nice ring when paired with my lastname. I looked up the meaning of it and it said springlike or full of life. He was later diagnosed with autism. My second son, I named Voltaire, supposedly after Voltes V. He turned out to be witty like his namesake (Arouet's pen name), the revolutionary French philosopher who introduced to the world the modern concepts of freedom we now get to enjoy. He's so smart (my son) he got bored in college so he took a leave (not a smart move).