Adding activities to Micro Entrepreneur

I am doing pet-sitting (using the ME business structure) and I would like to add more activities.

One of my pet-sitting clients needs help with activities in (and related to) her home, because she is becoming less physically able to do them herself.  The jobs she would like to pay me to do include housework (such as cleaning), washing & ironing of laundry, shopping, garden maintenance (such as grass mowing, weeding, pruning of bushes/small trees), some small DIY jobs, and most-likely taking her dog for a walk.

The above is not a complete list of everything she might like me to help her with - it all depends on how her health conditions affect her now, and in the future. 

Also, if I’m able to provide these services to her, I want to be able to offer to perform them for other people (be they an existing pet-sit client, or not) because pet-sitting does not earn me enough to live off.

So, to my first question: How would you advise I go about this?

I have identified that the form I must use is probably cerfa_13905-04.  However, from other information I’ve read online, it appears that I can only add one new activity at a time, and some of the activities I’ve mentioned above have different APE codes (so they cannot all be classed as a single new activity).

Also, I’m aware that I will need to specify which is my main activity.  Currently, my main activity remains as pet-sitting, because I have yet to build up my business performing the new activities.  However, I could see how the combined earnings from the new activities could quite easily become more than that for pet-sitting, as I can charge for these services by the hour. 

So, my second question is: Do I just wait until the money I earn from the other activities overtakes what I earn from pet-sitting before declaring that my main activity has changed?

And that leads me to a third question: As many of these seem to be separate activities, will I need to keep track of each one individually?  For example, will I invoice (and declare) the money I make doing housework separately from that doing small gardening jobs?  And if that is the case, then would it only be if I earned more money doing housework than I was making pet-sitting (as an example), then I would have to declare that my main activity has changed from pet-sitting to housework?

Thank you for your advice, Valerie.