I am interested in estate planning including preparation for a will and living will for myself and my wife.

Some details,
1. I am a UK citizen, married to a Chinese citizen, and we are living in Rotterdam.
2. We have 3 minor children and would like to name my brother living in France as guardian and trustee for our children if we should die.
3. We have purchased a house in Rotterdam.
4. The majority of our assets are in France.

Is it possible to prepare above wills and living wills and what is estimated cost to do so.