Should I opt for the regime fiscal micro?

I moved to France 2 months ago and am trying to set up as an auto-entrepreneur using the online registration website (haven’t actually completed it yet). The one particular question I am stuck on is do I opt for the regime fiscal micro or would I be better off paying income tax one year down the line?

The business I am setting up is a geological consultancy, mainly working from my home in France but possibly travelling overseas a little bit as well. I have selected Activity Liberale as my activity and Activites specialisees, scientific et techniques diverses - do these selections sound correct to you as there is no catogory for geological consultancy?

Regarding the option fiscal, If I opted to pay my income tax one year down the line would I declare it for the first time in May 2012 or May 2013? I am entering my start date for my business as the 1st October 2011 and I understand I can back date my application by 30 days - please correct me if I am wrong. So 2011 will only be a partial tax year for me.

I expect the business to make less than 10,000 euros between October and the end of this year but would hope that between Jan 2012 and December 2012 it would make somewhere between 20,000 to 30,000 euros for the whole year. I will have no other income and so based on what I have said, should I opt for the regime fiscal micro or not? I am married with two children.