CA3 is always a little bit of a problem. Candidates who have already attempted CA1 or a ST subject will have an advantage, because they will have developed skills other than technical. The CTs are a pre-requisite, the exam could draw on basic knowledge of any of these. Preparation for this exam is recommended at abot 50 hours - so whatever other subjects you take on, CA3 should not be too onerous to add on top - just another couple of hours a week. Also, given the pass rate, it is likely that the average candidate may take 2 or 3 attempts, so I reckon you should take it as soon as you've got a good chance. I.e. perfect to sit alongside CA1.
As for CA2....
Well, If you can book your exam for say October/November, then it will not clash with April exams. Preparation is only 20 hours - and it shouldn't take more.
CA1 is such a long course (effectively a double) with so many new concepts, that it is not unreasonable to suppose you might fail at the first go. At least taking CA2&3 in the same sitting will give you a chance of getting a pass so that feel you are making progress.
Each to his/her own - all roads lead to Rome. Or is it that the road to hell is paved with good intentions?