Originally posted by bleuwater .... I will be using this camera mainly for family photos, mostly of my toddler, and travel photography.
I was in a similar position as yours about 3 years ago, when I bought my K-7. Then I wanted a system (camera + lens) simple, convenient, covering all my needs with minimum number of lens(es). My two first lenses were (1) an all-around lens and (2) a fast prime lens. The former is very versatile, flexible and the best way to enjoy travelling in family without a bag of lenses. The latter is a bit more specialised, but very useful to take pictures in low-light: e.g., indoor, at sunrise, sunset... In that sense, I tend to agree with Adam, although I think that there are a few more options
So what are ther options?
(a) New lenses
If you want to buy new, your best choice is IMHO:
DA18-135WR and FA50mm f1.4
A cheaper options is the DA18-135mm WR and F50mm f1.8
(b) New and Weather resistant lenses (both)
The first (a) option had only one WR lens: the DA18-135mm WR.
A WR fast lens is the DA*55mm f1.4. It is more expensive than the DA50mm f1.4 (or F50mm f1.8). It is also a nice lens with great IQ.
(c) Second hand lenses
A third option is to buy second hand the lenses and you have a broader choice.
There are several all-around lens options, the better ones being the Pentax DA18-250mm, Tamron 18-250mm and DA18-135mm IMO.
For a fast lens, you have a very broad choise and then you may need to consider if you want a AF or MF lens. MF lenses tend to be cheaper. Check the Pentax user review section of PF for some user feedback on various lenses.
What would I recommend? In my case, I bought second hand the DA18-250mm and the Voigtlander Nokton 58mm f1.4. That is, I followed option (c) after doing my homework. I love both lensesand they are still my most used lenses.
Hope that the comments may help.