I am on day 12 of 21 and this is my second MC, so I am certainly not an expert.
Having said that, I don't believe that there is necessarily a right or wrong way to go on this. If you're feeling great and your body is willing, then I would do it.
By drinking the lemonade your body is getting the nutrients it needs to function properly. I think you would be fine to go ahead, unless you started feeling crummy and felt the need for food...more than just the usual hunger pains.
I would recommend a P & B cleanse if you are feeling the need to get out more toxins. This will enhance the benefits of the MC.