Im doing mostly maths and chem revision these holidays. I do art so im working on my major work along with that.
How im approaching the sciences is basically finalising notes on module 5 or whatever module was done during term 4 last year. And then starting on mod 6 content (especially chem - idk about your school but mines doing a titration prac assessment, so getting familiar first with acids/bases and all that so it is easier when you get into the term).
For maths, im working through the textbook - again depends on what your school is up to, but im just getting ahead kind of 'studying' for next terms math assessments (for advanced im doing graphs and derivatives which is chapter 3-4 on the cambridge textbook, and for extension is induction and vectors). It would help if you knew what topics you are being tested on next term so you could start with those. otherwise solidifying all the content from last term and filling in the gaps as you obviously will be tested on them for trials and hsc.
Lastly, im not too stressed for english - my approach is reading the books and doing any set holiday hw, which for me is writing an essay. you could also do practice for unseen text analysis (which you probably were tested on during prelims).
hope this helps...