Schools are generally good - and you'll find a lot of the kids in primary particularly are ahead of the UK. If you are interested in schooling, then The My School web page (www.myschool.gov.au) gives the results for each school.
Mindarie is a bit poor for transaport; nearest train station would be Clarkson. It would be a 35 min train ride to Perth CBD. Marina is quite nice (Indian Ocean Brewing Co. is excellent) and the area is generally safe, with a good shopping centre at Ocean Keys which is currently being expanded.
No idea on rentals, but try http://reiwa.com.au/.
Mindarie is a great place to live, the Marina is on your doorstep, beaches 5 mins away, playparks for the children are great, the best one in Mullaloo which is a drive but is well worth it. Shops within a few minutes driving, so groceries, DIY, bakers etc etc
Best School by far is Mindarie Primary School and I really mean 'By Far'. There are 172 Expat families here and plenty of support from everyone to welcome you. You will need to live within a specific catchment area for your children to attend, you can get that from their website or by calling them for info, they are all very helpful.
Prices of rentals depend on what you need. You can find a nice place with a pool for around $600 per week but you can go luxury end and spend $1,550 a week depending on your budget.
David Evans has quite a few rentals on just now with a really nice one actually overlooking the Marina for a very reasonable price.
Lots to do and see for the kids, mainly down on the beach or at home around the pool with friends. If you haven't got a pool, make friends with someone who has, its really needed in the summer to cool off.
If you have a car, transport is not an issue otherwise you can use the local bus for a very few dollars to get around. Public transport is cheap compared with the UK. Also, the pace of driving is very much slower and the freeway is maximum speed of 60 miles an hour so a lot more relaxed.
Are you bringing furniture? If not, I can suggest quite a few places to get you started which have really good prices.
What industry are you coming into? What visa? 457?
I can suggest a really nice place overlooking the ocean in Quinns rocks. It's $100 a day but is fully furnished and owned by a very nice lady who rented it to us for our first 2 weeks here until we found our own house. It's fully furnished and all bills, lecky, water, gas everything is covered for the $100 a day.
Good luck and if you need anymore info, We will help wherever we can
John and Lisa