DD (almost 12 at the time) and I were there last May. If your DS is afraid of big drops, I would avoid MOST of the big coasters at BG.
Sheikra is very high with an intense vertical drop. Took me more than a day to work up the couraage to ride it, but I loved it when I did! He will probably take one look at it and say no.
Gwazi... can't comment, didn't ride it as I don't like wooden coasters.
Montu.... my favorite coaster at BG, but again, VERY HIGH!! And lots of drops, corkscrews, inversions. Not the highest coaster, but intense in its own way. Very SMOOOTH.
Kumba..... one ride on this made me VERY queasy (yet multiple rides on the other coasters didn't bother me at all). Can't remember much else about it.
Cheetah Chase and Scorpion.... much milder. I suppose you could use them as a test (i.e.... if he does okay on these, he could try another).
Anyhow, if he hates big drops, I would definitely avoid the big four I previously mentioned. They will still be there when he is older...........P