This is 'guilty until proven innocent'. Unfortunately once your family is in the grasp of agencies like CPS, it is very hard to get out of it. If you had more money I would suggest to get the advise of a lawyer before you say any thing more to CPS. There is some general information on the web in terms of what your rights are and it is important to find out what they are.

I am not sure they are within their own regulations to investigate you for this reason alone. Are they investigating everyone in Texas who has under age children and leaves a psych ward?

I believe they have to have a specific accusation to start an investigation and enter your house. They cannot enter without your permission without a search warrant. If someone claims to be CPS says they have a warrant, ask to see it. Did you ask them if you have been accused of anything and what specifically that would be, in detail? You have a right to know exactly what you have been accused of.

A lawyer would be in the best position to guide you now in order to advance your interests.