Hey!
I have jotted down my thoughts below:
1) Your preference of schools depends on a host of factors which you need to first take a call on: importance of brand, ROI, location, where you want to live/work post-graduation, post-MBA industry, duration of the program, preference towards diversity (usually Europe) or studying in the country where MBA was born (USA) etc. Once you have decided (more or less) on these factors, only then can you make a more informed assessment of which colleges to target. My suggestion would be to do this as soon as possible (ideally in the next week or so). Talk to friends and acquaintances and read up on current business trends if that helps.
2) As for taking GMAT in August, my suggestion would be to work on applications simultaneously with preparing for GMAT. I understand this could get very tough with your work schedule, but think of it like this, with right time management and prioritisation for two months, you could potentially be sitting in your dream school next year
3) To make life easier, you could potentially also take help of admission consultants. This is a highly personal call, however, I am stating it just to bring the point out that we don't need to make everything in our lives difficult when there is a potentially easier way out. A right consultant could help you ease your schedule, tend to your worries and keep you on schedule over and above the usual services they provide.
All the best!