Answer: Yes, you certainly can use McKinney-Vento funds to provide transportation for parents experiencing homelessness to attend your parent group. That would fall under this allowable use of funds from the law:
“(10) The provision of education and training to the parents and guardians of homeless children and youths about the rights of, and resources available to, such children and youths, and other activities designed to increase the meaningful involvement of parents and guardians of homeless children and youths in the education of such children and youths.” 42 USC §11433(d)(10).