Cute. I like them. Although they are plainer names in general, I have always thought
Kate is beautiful and
Jane is spunky (especially on a little girl!). I love them together, too.
For middle names, I would suggest more uncommon names to set apart the common first names. How about:
Kate NatalieKate PhilippaKate VictoriaKate AlexandraKate ElizaKate Rebecca
Jane VictoriaJane LillianJane AlexandraJane AmeliaJane RebeccaJane Charlotte