Just so you know the Gates of Lodore Trip on the Green is high right now at 4350 cfs. The Yampa is really high at about 12,000 cfs. I've only done the Gates of Lodore at low flow at about 900 cfs and it was really technical. At high flows all of those will be covered and big hydraulics will develop. Make sure everyone has guidebooks and knows where they are.
Below the confluence are some pretty good rapids especially in whirlpool canyon where there are...you guessed it....lots of whirlpools. Especially at 16,000 cfs. I've done the Yampa at close to that level and it's big and pushy. There is nothing technical. Kayakers with a weak roll or weak bracing skills will have trouble here. Other than eddylines, I don't remember anything big enough to flip a raft below the confluence.
You might want to monitor the Yampa Flow at:
Unfortunately, the publisher of the only good guidebook for this trip is reprinting the book. It should be available in early June. So your only shot is to find it at a local shop if one has some left. Otherwise, once it is in print again you can find it here:
Have fun on your trip.