i have only attended hhn the first 14 days of the event, never at the end as the crowd level is too great.
with that in mind, i can only say, if it was me, i would chose the thursday and definetely avoid the friday, saturday and monday the 31st.
if you buy a multi day ticket for the daytime, you can buy the ADD ON for the hhn ticket. it is cheaper. go in the daytime, stay in the park at the designated stay and scream area, and be able to start the hhn event at least 1 to 1 1/2 hours before the general public gets in at 7.
i suggest that once you know the date or dates you plan to go, buy the express pass then. they do sell out. do not wait to buy it at the gate since you are going at the end of the month. buy it in advance thru the toll free number. only a limited number are sold per day over the phone. if you call and are told they are out of them that day, call back the next day.
OT: honolulu eh........my brother lives there since 1988. it's a great place to go visit family. beautiful place.