Sorry - but you knew it was wrong so beyond you not getting a 1 year reprimand what would counselling achieve. Counselling is basically telling you how to do something correctly because:
1. You did not know the correct method.
2. You had not been trained to the correct standard
3. You were not doing the task at an acceptable level.
You quite clearly state you knew you were doing wrong, and no doubt had been made aware of at an WTL. The manager would have been aware of that and had a paper trail to prove it. It has since its introduction been a conduct-able offence to not use the appropriate equipment and a 1 year warning is probably the lowest punishment you could expect.
What you should have done was advise them as per the rules about being unable to complete the delivery and let him make the decision. If the discussion did not produce the results you wanted or they refused to manage the situation then you should have contacted the CWU Rep/Bolshy mate, and got their help.
With Child care problems and "flexibility" a decent rep should have been able to get some of the work covered for you and the manager if he was aware of the situation should have done it without pressure from the rep. Flexibility can be asked for by workers as well management and you could have finished 30 minutes earlier and made the time up later in the week, with childcare issues this would have been an ideal solution for both.
I know that it can be frustrating and intimidating advising the manager when you can't complete and you have my sympathy, but now you can see the pitfalls of making your own decision without authority. My advice would be starting playing the managers by the rules.