There are a lot of biting insects in Florida, and many people can have a reaction to those bites ( I know because the mozzies LOVE me and I react to their bites). There are a number of questions that need to be answered.
1) Was it 100% certain that it was bedbugs that caused their bites?
2) did they only stay at a Disney hotel
3) how bad were the bites, I know they are unpleasant but it's unusual for anyone to be badly hurt from this.
4) did they complain while they were there? or did they wait until the end of the holiday or when they were home? If they told the hotel I can't believe the hotel would do nothing about it. Getting the room/bedding treated would get rid of the problem immediately.
5) If it was an on going problem,why did they continue to stay in the room? I can't believe anyone would put up with this type of problem for any length of time.
If Disney didn't offer compensation then I would be certain they feel either they were not informed, or that they dealt with the problem appropriately. Florida's climate means there are lots of insects, IMHO someone is hopeful if they expect compensation for getting bitten in anything other than exceptional and unusual circumstances.