When we were going I know they had reservations at Yak & Yeti until at least 15 minutes before closing. Plenty of people will be still dining when the park closes. They won't push you out by 5. On the other hand, I doubt there'll be any reservations for in park restaurants much more than 15 minutes or so after official closing time. You can go to the dining reservations page and put in your info (restaurant, date, time) and see what comes up.
Rainforest has an entrance outside the park turnstiles so I don't know what their policy is.