Outside scholarships that provide a significant amount of aid are rare.
Also attending an out of state school for a program that is mostly likely available in your home state is not a great idea if you are looking to minimize costs.
Some private colleges actually end up being less expensive than public schools if your child has high stats for the school.
Most people here on CC are helpful, but we’d need more info about your kids stats (gpa, test scores, ECs, etc) to give you the best advice on possible merit aid opportunities for your kids. Would you be willing to share those here?