My DS10, soon to be DS11, took an Intro to Python programming course from AoPS this summer and it was run very similar to the Geometry course you describe. The course was pretty tough for him and I contacted a local university and found a tutor which turned out to really help (as I was of almost no use to him). He now often likes to find difficult math problems and write code to find the answers.

He is currently working with EPGY Geometry and is definitely being challenged. It has been a long time since I took Geometry and I do not remember being presented with some of the topics in such great depth. In the past year he has completed EPGY's 5-6, PreAlgebra, Algebra and Intermed Algebra. Geometry is the first course that has really challenged him but he seems to be rising to the challenge so far.

I think we may try the AOPS Counting and the Number Theory classes after he finishes Geometry. I was thinking of trying to just get the books and go through it without the online course but not sure how that might work.

Thanks for the info on AoPS Geometry.