Best setup for a cross-border freelance business in France?

We are returning expats looking to set up a consultancy business in France, working primarily from our owned residence here in France. My husband is British and I classify as a non-EU family member with a titre de sejour (toute activité professionnelle) valid until 2019. Our business is in marketing and communications and initially we are looking to service clients in Asia, the UK and Switzerland.

While we both work in the same field we will, more often than not, have separate clients and separate projects. At the moment, we are working on the assumption that we will fall within the micro-entrepreneur business threshold, with the possibility that we may go over should we secure more business than projected.

1. What type of business legal structure in France (there is a possibility that we may go over the micro-entrepreneur threshold) should we have for our business given that we share the same field but will have mostly separate projects? Would you recommend we apply as 2 separate micro-entrepreneurs?
2. How does having three children affect our health cover/Carte Vitale in terms of social security/tax contributions?
3. What are the tax implications for doing work for clients outside of France, i.e. Asia, UK, Switzerland?