I should also mention that the plaintiff in this case might want to consider small claims court. In Florida, the dollar limit for small claims is $5,000. The plaintiff will have to pay a small fee to file the claim and also pay for Service of Process (i.e. the summons which will be served on Disney).
Once Disney receives their “Notice to Appear”, they’ll try to settle the case before it goes to trial. If their offer is refused, they must go to the pretrial hearing. At this point the judge will often order that the case go to a mediation conference. If that fails, the case goes to trial.
I can tell you that most cases don’t go to trial. Disney always prefers settlements for obvious reasons (public records and adverse publicity make Disney very nervous).
You might advise your SIL that pursuant to the Florida statute of limitations, claims for injuries sustained by a minor must be brought within four years of the date of the injury. Your SIL still has plenty of time to file a claim.
She might also want to try a more direct route and just contact Disney and suggest a settlement amount. A two week all expenses paid trip to WDW would be a good starting point and seems to be in line with the wishes of your SIL. Under the circumstances you described, I think Disney would consider this a reasonable settlement.