Hi there DaveC and welcome.
To be perfectly honest, I'd just continue with the mainstream series and leave the 'Science' books until you've finished.
I don't think you'll gain anything that you don't already know about the Disc from them. The Science series have short bits with the Wizards, but they are mainly looking at Earth science through using the wizards. The majority of the books are written by Jack Cohen and Ian Stewart with Terry's collaboration (I think I'm right in saying).
I hope that helps.
I have to say that I've only read the first 'Science' book and didn't enjoy it much - too much science and not enough Discworld.
“Men never commit evil so fully and joyfully as when they do it for religious convictions.” – Blaise Pascal