A few thoughts, but firstly I have no experience with the Sigma or Tamron lenses but am sure someone will come along who does!
Anyway, you say you're considering replacements for the kit lenses, but you're happy with them? The 16-45 is better IQ wise than the 18-55, and contant aperture (f4), so some advantages, and won't break the bank. BUT, it'll only replace the 18-55. The Pentax16-50 is supposed to be good, but has suffered with SDM issues (hopefully now resolved), and the Pentax 17-70 is also highly rated.
The 55-300 is regarded as better than the 50-200, so potentially improved IQ and range, which could be good for longer range candids of the kids.
The 35's will give you equivalent fov on your K-x to the 50 on a full frame, so good for portraits. The 35 f2.4 is considered to be great value, but not as good IQ wise when compared with the Ltd.
Landscapes - I use a Pentax 12-24, and it's great. That said, went on a course recently were I was persuaded to use longer lenses, which although counter intuitive does work, but there's always room for a UWA lens when you want to capture a 'vista'.
Macro. Unless you're doing still life I'd suggest the longer the focal length the better because it gives you more working room between you and the subject. With a 50 macro you'll be right on top of the subject.
If I were you I'd pick just one area of photography you want to concentrate on and buy your next lens for that purpose; there's always future birthdays, Fathers day, Christmas