So, you want to do chem eng. and science, a very popular combination. Let me explain a few things:
From the course planning perspective, maths is always going to be in there [you have to major], and you have room for another major, and that's it. You don't have room for another minor, you only get to study two topics at the second and third level. You do have some leeway in first year though, and that is one set of electives.
If you choose to major in chemistry [and you would want to if you picked 'chemical engineering' for the chemistry, because there's not much], you would want the other first year sequence to be physics, especially if you haven't done year 12 physics. Newtonian physics will bite you like a bitch if you don't. The physics department is so shit beyond description, but you'll still need the knowledge.
If you choose to major in physics, lucky you. Enjoy the worst physics department ever for three years. Menzies is quite tall, feel free to jump off it.
If you choose to major in something else, good for you. Make sure you brush up on your statics and dynamics because you won't be able to fit physics in there.
If you don't like maths, stay clear of engineering. Do biomed or something where you don't have to worry about numbers.
As for the engineering side:
In first year, you are going to be breezing through it. Anyone with a bit of computing background will kill the computing unit, anyone with a bit of math background [chemistry isn't even needed] will kill the chem eng unit.
In second year, shit will go down. These units are much harder with a much higher fail rate. Even if you were a high achiever (99) at VCE, you're probably only looking at ~60 to ~70 for these units, about a third of the cohort repeats.