ACAS have a helpline for employees which you can google online.
Your employer can ask you to make a statement and it is in your interest that you do. It is a normal thing for them to ask.
Essentially, it's an error which is in the grand scheme of things not a big one.
If the family wanted to sue then it would be against the hotel but I doubt very much that they would as unlikely that a solicitor would act for a very small error- it's not worth much in damages. The hotel may offer the family some compensation off say some vouchers or money off their bill.
Try not to worry though.