Family info doesn't belong in any interview for any job. Don't discuss your children or special needs - that doesn't necessarily qualify you to be a good para aide, and the absence of children doesn't mean someone wouldn't be fabulous in the job.
Dress? Nice slacks and a nice top, or a skirt/top. Nothing revealing, nothing highly constrictive. I don't think you need a suit, but I wouldn't wear jeans either. Decent flats or low heels would be best - be comfortable.
What you should be highlighting is your experience as a volunteer.
What IS relevant about your family is that, if this is the same school where your children are enrolled, is discussion of how you will handle being in the same room as your kids (highly undesirable) and how you will transition to a professional vs. social association. You'll be exposed to confidential info (behavioral, intellectual, medical, developmental, social) about kids whose parents you know or who may be in your kids' social circle. The panel will be looking for things in your answers or demeanor that indicate you can separate your social life from your professional responsibilities.
Good luck! I hope things go well. Just try to relax and really listen to the questions. It's okay to pause before answering.