LICENSE BEING SUSPENDED

We live in Florida and my son is 22yrs old, lives with me & had basic car insurance under my auto policy.He is currently working full time but will be enrolling in college soon.He lost his brakes while driving his vw jetta & hit a couple driving an lexis SUV.We saw when the female was picked up by the ambulance.The only noticeble damage was the front bumper came off.My sons car was very badly damaged but after 3mths was but back together by his stepdad.The problem is the state of Fl will be suspending his license if he doesnt pay $1,100.deposit.Supposedly there was $500. of bodily injury between the couple & after our insurance paid there is still another $600. for property damaged.We mailed a release form to the injured party required by the state of fl & a payment agreement but the couple didnt respond back.We also included a very nice simpity letter telling them how sorry my son was about the accident & that we hoped very much that out of the kindness of their heart they sign the release forms because we don't have any money. The MVD told us if the couple don't return the release forms my son has the chance to be sued anytime within the next 25yrs,The State of Fl will hold the $1100. for a yr & return this money if it isnt claimed by the injured party.We were under the impression that the injured party's insurance would cover what my sons insurance didnt pay because of his limited coverage.He now has an SR 22 which requires higher coverage for the next 3yrs.Being that he is under my car insurance would these people try to sue me since I own a home?Needless to say my son can't be without a license & will pay the deposit , which I'm sure it will be more than just a deposit.Is there anything a lawyer can do for us in this situation?Are there any other steps or procedures we can take to make the other party & their insurance understand we don't have anything to give.