I have kids exactly the same age as you.
1. Is it feasible and practical for both parents to be working, ie school runs etc,
Of course depends on where you work. My Mrs had her 'real' job for a while when we got here but canned it as she was finding it hard to do both that and the kids pick/drop (and she is enjoying the ladies that lunch scene far too much) The 8/3 age mix may be the issue. FS/Reception 1 usually finishes around 12-1pm and older kids 2:30-3pm. You may find that if your wife can get a teaching job at your kids schools you will get discounted school fees. This is what my wife does. While they don't get paid a huge amount, when you factor in the fee savings it becomes more attractive.
2. what age do young children start school in Dubai,
My youngest is 3 yrs 2 months and can start FS/Reception 1 in September. The year they are 5 the start year 1. THe oldest is 8 in July and is in year 3 and started year 1 when he was 5 and change. British school system. Nursery generally covers kids to year 1 and finishes usually at 3 with some staying open longer for office hours parents. Usually a tiered payment system depending on finish times. Most schools have after school club for the younger kids to align with the older kids finish times. This costs extra, something like 50 dingas a day.
3. Are there any schools on the complexes where emirates place families to live,
Dunno, don't work for Emirates but I know a few Emirates guys who live around Arabian Ranches and send their kids to the school there. I think it is JESS? Something like that. Very loooooong wait list though.
4. I have visited Dubai quite extensively and would be horrified at my misses driving on those busy roads to get to work and the kids to school !
The traffic is not as bad as you think. It is surprisingly efficient. Treat it like snow skiing where you just miss what is in front of you and let the faster people behind do the same.
5. And finally a topic that would be nice to know, would we both qualify for the housing and utilities allowance in our respective professions or can just one working partner claim it ?
Depends. Your wife can actually be a more attractive employment prospect based on them not having to pay allowances. Often schools have multiple apartments in a block for their teachers. Many companies want their name on the lease when paying allowances as well so if you have Emirates accom that may be difficult.
happy to answer what ever here or personal message.