@shuvayan
The best way to do Facial Keypoints detection would be through Deep Learning. So, it would make sense to look for resources on machine learning instead of just facial recognition. A good starting point is to do the Neural Networks course on Coursera, which is being taught by Geoffrey Hinton.
Here are a few papers, you can refer to, but they are not in form of a tutorial:
http://cs229.stanford.edu/proj2014/Yue%20Wang,Yang%20Song,Facial%20Keypoints%20Detection.pdf
Also, given that you would need to perform deep learning, it might make sense to try a few tools outside R. I have heard Lua Torch to be the most commonly used library for these computations. I read somewhere that Google, FB and the research group of Prof. Hinton all use Lua Torch for work on Deep learning - but I might be wrong!
Regards,
Kunal