First, are you flying? Asking because depending on how Irma tracks, it is possible MCO will be closed on 9/9. If you are planning on driving, again, depending on how Irma tracks, you may find evacuation rules in place that either prevent you from getting to WDW or having to deal with huge traffic issues.
Second, if Ira tracks into Florida it is possible WDW may close.
Third, food stores and gas stations in Florida may or may not have supplies on 9/9, which unless you are staying on property could cause problems.
Bottom line: check the cancellation/re-booking policies on your reservations and be aware the Disney phone centers are getting swamped right now (people are saying it took them hours on hold before getting to an agent). Keep you eye on the forecasts, which unfortunately suggest we aren't going to know until Saturday whether Irma is going hit Florida.