Don:
In reference to your question about clearing, I can offer some experience in certifying kids age 10 and up with SCUBA (I know little about freediving). As far as the equalizing itself goes, the kids I have taught pretty much mirror the adult population in ability. I have seen those that cannot seem to do it no matter what to those who effortlessly equalize with a swallow, and all points in between. Most of them, like most adults, need to do at least a little something to equalize.
The difference for me has been in the way I challenge them to continue trying if they have problems and the types of encouragement I provide. You have to be very patient with them and allow them to come to their own solution, while at the same time providing guidance on different methods and styles. The objective becomes to provide enough guidance that they learn to do it without hurting themselves or giving up completely. It sometimes takes multiple trips to get down the first time. The good news is, once they get it, they tend to get it good and don't have any problems after that. Couple of hints for those that have problems:
1. Start equalizing on the surface, before they go down. It can loosen up their Eustachian tubes.
2. Control the descent, use a line and go down very slowly and stay upright.
3. Equalize with them, in an exaggerated style. Even if you don't use the so called valsalva maneuver, puff out your cheeks, pinch your nose, bob your head, etc. Monkey see/monkey do: If they see you do it constantly, they will be more apt to do it constantly as they ascend.
4. Try to minimize a lot of up to the surface and then back down trips. If they need to ascend some because of pain, it usually doesn't need to be more than a few feet. If they become panicked, you of course go ahead and ascend.
One final note, I have noticed in the past (and it was recently backed up by a DAN article) that kids who have suffered from frequent ear infections at an early age seem to have more difficulty than those who haven't. I initially noticed this on my own kids. My oldest was in the hospital at 3 weeks for ear infections while his brother had a much easier time. The oldest loves to dive but suffers from frequent ear equalization problems, vertigo and reverse sinus blocks. The other never had much problem with it. My daughter, show I don't think ever had an ear infection, simply swallows and equalizes with ease. According to DAN, it may be that scar tissue and damage from frequent early infections may be at the root of the problem. Additionally, it is thought that the same physical features that make kids susceptible to infections can also make equalizing tough.
This is just what I've had experience with. I'd love to hear from other folks with experience working with kids and equalizing.
Best of luck.
Joe.