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Time crunched:
Your swimming is good already, so don't bother swim training. The marginal gain from improved swim time is not worth the training cost. Do some kitchen / bath transitions, taking your wet wetsuit off.
Cycling: stick with the commute, or a weekly longish ride* - All of your gains will come as a side effect of:
Running: focus on run training. Find a half marathon / full marathon plan that fits your schedule.
* make them brick sessions as your training volume increases.
Let me rephrase that, any time crunched parents that wanted to be competitive in a 70.3 got a tried and tested targeted plan?