Well, it depends, do you like to be scared ? Do you like horor movies ? In my opinion, Halloween Horror Nights is AWESOME ! But is just that - Horror ! It is a PG-13 event & may be to intense for children. The park (
HHN is in IOA this year) is normal during the day, & shuts down for the "transformation" at 5 or 5:30pm. They then re-open for HHN at 7pm. They completely change the "feel" of the park & turn it all spooky with fog & creepy music!! (yes, really thick, can't see your hand in front of your face fog) There are haunted houses (5 last year) & different shows specially done for HHN.
"Scareactors" at every turn & haunted houses in almost every island. Most all of the attractions are open, (except those that are being used for a haunted house) and last year HHN was open until 2 am on peak nights, but the coasters closed down at 11pm or midnight.
My opinion, YES ! it is worth the money
It is a seperate ticket & you can't use your day ticket to get into HHN. It is also date specific & they do tend to sell out quickly.
Look for discounts - there is a discount for Florida Residents, for the Fan Club Card, for annual passholders & off peak nights are cheaper than peak nights.
Hope that helps !
Haggy