I'm in Dubai which is 150 km down the road but same difference more or less.
In summary - kite all year round, water temp from 22C in the winter to 35C (yep!) in the summer. Weak winds on average but kiteable. Need a large kite and board most of the time. Between November and May stronger winds come down from the North of the Gulf (known as 'Shamal' winds from the Arabic work for North). Usually appear for 2-4 days once or twice a fortnight and can vary between 15-25 knots. Inbetween them its rubbish with 6-10 knots. No waves to speak of in the Arabian Gulf. Fantastic windy season 8/9 hours drive away on the east coast of Oman (south of Muscat in Aseelah) between May and September. Winds of 20-40 knots. Good waves too. Back in Abu Dhabi/Dubai the May - September period has consistent 8-12 knot sea breezes and it is hot as hell.
Quite a few beaches in Abu Dhabi to kite but let's be honest. The wind sucks here. No sharkies. Quite a number of Abu Dhabi kiters - just get your brother to post on http://www.dubaikiteforum.com and he'll no doubt be able to find a few chums to kite with.