Let me suggest a few things. First, having some teaching experience is useful for most beginning academics. So a TA has value in itself. It shouldn't be hard to "sell" that. However, the professor now funning you has no input into who is a TA. That is normally a department decision. You apply there for a position, not to a particular professor. You may have little control over your schedule as a TA, but it will be fixed, at least, so perhaps you can work around that.
Next, your relationship with the professors needs to be managed separately. They are probably depending on you for important work. If you just quit the project they might be unhappy enough to negatively affect your future, at least in the short term. But having family responsibilities is a reasonable enough reason for changing things around. But you should, I think, negotiate an exit, leaving the project in a good state. You want their attitude to be "Sorry to see you go, but we understand."
I would talk to whoever in the department is responsible for TAs first, so that you know whether a position would be open to you. In some fields (math) there is usually a need for lots of TAs. But you would probably be assisting in lower level courses, which might be a bit boring. That might be good, or not, depending on your other responsibilities.
And these are the kinds of discussions/negotiations that need to be done face-to-face, not by email.