I dont foresee any problem with a fire cracker causing any real damage to your home what does your realtor have to say?
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I'm not sure who wants you to sign the disclosure, or why they'd want it. But as far as resale goes, you'd have to disclose anything that could be a 'material' fact to the buyer. In other words, something that would sway their decision one way or another, or something that could be a problem in the future.

For instance, you have to disclose if there has been a flood in the basement, because mold spores could have gotten started, and they could crop up again if they come in contact with moisture again.

If there was an actual fire, that's something that should be disclosed. Fire can affect the structural integrity of a house even if the charred parts are replaced.

I really can't give you more advice than that, because I don't know what the person who's having you sign the disclosure plans to do with it. Maybe it's more of a release form?

Your agent at the time you sell could advise you better. As far as whether or not to sign the form, what happens if you don't sign it? If you do sign it, you should speak to an attorney first.