We want our site to be a comprehensive guide to climbing with kids. Our product reviews, while we hope they are helpful, are not comprehensive because they include only those products that we have personally used. The information here should be more helpful in providing you as much useful information as we can to make a decision.
If you are in the market for a harness please check out the article below written by a climbing gym in the UK. While you might never climb there, they provide an excellent source of information as to when to use a full body harness vs. a sit harness, what the leading designs are and why, and additional tips in choosing the right one.
I would just like to stress what was mentioned in the article that the Edelrid Fraggle II is the harness for the smallest kids. If you want something for a 2-3 year old to swing around in and start to climb then you are probably looking at getting their size XXS small. You can check out my review of it here and my review of the Petzl Simba here.