I'm guessing you'll be there at the end of November/beginning December? I guess crowds won't be too bad then. We're going in October and this year we WILL be there early, and we'll head straight for Rhino Rally.
Lines have been 45mins ++ the last times we've been (also October) so have never been on. Conversely, the Montu and Kumba lines were pretty short throughout the day.
Rhino Rally is a safari- cum- oh-no-something's-gone-wrong-raft ride.
Kumba is a fab coaster, and Montu is even better (inverted). Gwazi are two wooden coasters - Tiger and Lion. I find these more scary than the shoulder restraint ones, even though they don't go upside down!
The smaller coasters are short and painful (according to my DS) so grandma wants to avoid these even more than the big ones!
Congo river rapids is a raft ride like Kali at AK - great fun and you will get soaked. Stanley falls and the Tanganyika Tidal Wave are flumes - more opportunity to get wet.
Kids will love Land of the Dragons. It entertained a 3, 7, two 12s and a 15 year old for ages. A cross between Shamu's Happy Harbour and Fievel's Playland with little kiddy rides and MORE opportunity to get wet!
If you like birds don't miss Lory Landing. Buy a pot of "nectar" for $3 and have the birds land on you to feed. And visit the nursery to see cute and not-so-cute babies.
You get two "free" beers per adult at the Anheuser Busch hospitality centre. Good pizzas available here too.
Enjoy!