-What will crowds be like?
-Is there any certain order we should travel the parks?
-How close are the two parks together?
- Any interesting tips/hints?
I haven't been to the water park, but BGA has been very busy due to the many South American tour groups. These groups seem to be larger than in the past, so if one descends on a ride, be prepared to wait unless you purchase the Quick Queue, which is about $25.00. (If you're lucky, they'll be at a Disney park on the day of your visit, so you won't have a problem).
If you want to do the coasters, my advice is to get to the park when it opens - usually around 9:00 am. If they do their staggered opening, you'll be able to do Montu and Gwazi a couple of times. Then you can head over to Sheikra and Kumba. The lines usually don't get too bad until around 11:30. You might want to check their operating hours so you can plan your days. Keep in mind, it has been raining almost every day and that can impact your visit since they close the rides during a storm.
Hope this helps - have fun.