hey,
It wouldn't be too late but you'd really have to decide soon...
Looking at EE2 alone I'd definately say do it, because I loved it and it was a subject I really enjoyed because of the freedom and the independant research etc. Though, not dropping a subject isn't such a good idea, firstly overlooking is probably worse than dropping...and not all that smart if attempt to choose a subject not to count for a UAI (assuming you want one) because with that logic there is no point taking it on at all. I did 13 units in yr. 11, but then dropped a 2u subject to pick up EE2, which left me on 12 units for the HSC. I personally think this is the way to go.
EE2 is a lot of work, and most of it would be in your own time so you really don't want to give yourself more than you can handle. If you want to do well less may be best, if you want to pick up EE2.
I did the HSC last year but when we picked subjects we were told that 14 units would be suicide and I have to agree...you don't need to put any more stress on yourself than necessary during the HSC.
So while I'm all for EE2 and would always encourage willing students to do it, if you're not going to drop any of your other subjects perhaps you shouldn't. Really think about it before you commit yourself.
Let us know what you decide and good luck with your studies