martinslade said:
I am thinking of expanding my photography ... to include natural shots of dogs and kids playing and possibly just kids playing. ... was thinking of getting a Canon 6D which will also shorten the tele effect. ... Is this a good idea or is there a better solution in this price range..?
The 6D is an excellent camera and a terrific value. I owned one from December 2012-October 2016 and it was my only DSLR for most of that time. As LesC pointed out, the AF on the 6D is pretty basic, there are better camera bodies available for moving subjects, but outside of the
much more expensive 5D MkIV, 1Dx or 1Dx MkII, its the best low light/higher ISO body Canon makes.
The series by Dawid Gaszynski in Sporgon's link show what is possible with the 6D in the hands of a skilled photographer even with the limited AF system.
You should also consider a 5D MkIII. Prices are coming down, but still nearly 1.5x or 2x higher than the 6D. With the 5D MkIII you get a much better AF system, but the 6D has a better sensor and higher ISO images are cleaner. So, as is often the case, there is no one best solution.
If you are not in a hurry, wait for the 6D MkII announcement to see if it might be a better fit for what you are looking for. I expect the Mk II will be 2x the price of the 6D MkI at introduction. I expect the 6D MkII will be better all-around than the 5D MkIII, but we won't know until its announced.