Where to find height dataset, or datasets in General
The Galton Height dataset seems to be exactly what you're looking for.

There are a ton of repositories of open datasets online.  For beginners, I often see the UCI Machine Learning Repository.  It has quite a few datasets which are easy to work with.

Some other resources for datasets:


Kaggle - hosts data science competitions, but you can download all the datasets without participating in a competition.
Data.gov - You can freely download data from US govt agencies
AWS Open Data - You need a AWS account, but these datasets are free-to-download