Good luck!
Up for the morning and bright and breezy (not) so can type a more comprehensive answer re school.
In your position, I'd get school places first, then worry about where to live
Are you looking for places in Y6 and Y3?
Something else to consider would be, if your oldest is now in Y6 he will move to secondary next year. The Alice Smith Secondary campus is miles away and that freaks some parents out, (its a good 45 mins from the primary, and wait until school ask you to come to an event at 7pm on a friday - it may as well be the moon!). Plenty of kids do it though (inc mine), they learn the art of sleep on the bus.
Other schools have just the one campus, which makes them very large. GIS put me off because I didn't like the fact than pre-school kids were on the same massive campus as 6th formers and the area is so built up - hemmed in on all sides by high rise condos and highways. (we had come from a one form entry village school in the UK and it was all a bit of a shock!) Alice Smith Primary is in a greener area, and despite being a five form entry, still feels like a "British village school". ALso the admissions person at GIS was really bloody rude (as if she was doing us a huge favour showing us around), but this was 2003, so likely not a problem anymore.
When I first arrived in KL, those were the only two choices, but there is now ISP (Desa park City school)-a new school, and still untested as far as results go. Their first cohort of Y11 are sitting GCSEs this year. It has a nice atmosphere, lovely staff, but it's location is not great (unless you live in either DPC itself or Valencia (or one of the other gated communities around Sungai Buloh)- this puts your dh a good 45 mins out of town, going with the traffic both ways could easily take 90 mins. (no train).
British school I don't know a huge amount about but its location is also not fantastic (Bandar Utama), but its fees are very high, and the general consensus is they are overcharging for a largely untested school (no GCSE results yet)- they do have an amazing campus and shareholders to pay for though. Headteacher has a huge chip on her shoulder if anyone compares them to AS.
IGB I know nothing about, except its new and and not far from DPC/Valencia. Fees look hideously expensive for a new school.
Unfortunately, arriving when you are at short notice, you might have to go for where you can get a place.
Please do avoid the following though:
ELC (Sungai Buloh)- claims to be an International school, but in reality a very strict old fashioned private school, ruled by the iron fist of its owner. High staff turnover and poor facilities.
HELP International school - new campus but poor admin organisation, poor location, poor teaching staff - just poor in general apparently.
Fairview-treat their teachers appallingly, atrocious management, chaotic enviroment
In the event of not being able to get into AS, GIS, BSKL or ISP, you could look at Tenby school in Shah Alam. Not used by a huge number of expats (mainly local parents) but I hear mixed reviews, some great. It could be a stop gap school while waiting for one of the other schools. If you go on a waiting list, if you are UK passport holders, you should get priority at AS (but you might still be looking at a wait).