'Ohana has become one of the hardest restaurants to get into for dinner. Hopefully, you'll get the time and date you want on your first try. If not, keep checking online frequently between now and October because people change their plans all the time. 'Ohana gets very busy on Saturday nights and might be running behind schedule so I would recommend a reservation around 6:30 - absolutely no later than 7. You can always walk around and enjoy the resort if you finish dinner early.
Rainforest Cafe doesn't release all of their reservations to Disney so it often looks as if none are available. You can call the restaurant directly closer to your holiday or once you get to DW to make a reservation. There are 2 RFC at DW; one is at Animal Kingdom and the other is in DTD.