it is a relatively common practice in UK and other EU nations for young families to live in squats, and to take them to festivals. The children are protected by the same human rights laws in all 27 nations whatever lifestyle their parents lead. I can’t say how safe they would be in countries outside England as I do not have kids and have not been into squats in other nations.
I have however seen comments over the years from French people that there is a big hard drugs problem in some squats, anc occasionaly they are prone to vigilanté action from the hard right wing. That said, the problem isn’t when you have a little baby or small child. Even in the worst areas, communities look out for and look after a baby or small child. if we didn’t humans would be extinct now.
Where the problem occurs will be when your child needs to attend junior school by law (moving around loads means he/she has to keep changing locations and friends), and then when they reach pre-teen age and become curious about drugs use.
I would try and find a stable location with a good education for the age when your child needs to attend school. Hopefully the EU and Schengen agreement will last out until then!
