Someone recently asked whether or not it is a good idea to have well-heeled in-laws pay for an autistic child's home therapy program when public (school district or regional center) funding is available. Here is my reply:
My first thought would be to take your in-laws up on their offer. Private pay often affords you more control and flexibility (i.e., if you do not like the agency's approach, you can take immediate action; if a wonderful therapist feels he/she may leave due to cost of living, you may be able to offer them a raise), and you may be able to transition to regional center or school district (SD) funding later. We did private pay (thanks to fairy grandparents) for three years before transitioning to the school district. Because we had a truly fantastic, well-documented, established program, the SD agreed to take over funding rather than disrupt our son's program and life. We feel extremely lucky.
However, my in-laws are tolerant, trusting people who feel that those on the front line -- my husband and I -- are the experts. They wrote the checks and read the reports, but never imposed themselves on our program or decisions. If your in-laws' financial help comes with their intolerable interference, it may be better to go with regional center funding. (Though that also usually means a big struggle.)
Another thought is that your in-laws may be able to help you out with respite/babysitting that is completely separate from your therapy program. My in-laws still pay for a "babysitter" (actually a behavioral pre-K school teacher) to come for a few hours a week to do "engaged play" with our son, to follow his lead and keep him interacting in the less structured real world outside of therapy.
Good luck, and please keep reaching out when you need to.