Got any idea where exactly you want to live? First I suggest you decide between east or west of Malaga. They are two very different areas. Very roughly, it depends whether you want 'ex-pat' (west) or 'Spanish' (east) living?
Next you must decide whether you want to put your children in a British International school, or a Spanish one. If your kids speak some Spanish already the latter will give you a lot more choice on where you live. If you know you need a British school there is one (where my son goes) in Almuņecar, 70mins drive east of Malaga airport, and about five more to the west, stretching from Torremolinos to Estepona. Be prepared to make appointments to go see them all and troop around before deciding.
You won't find a long-term let on a flat until 1 October. Expect to have to put up with short term (high cost) rent if you move down before that. The Brit school year starts in early September.
PM me if you need more.
Dantruck