There is a $25 per night price difference for preferred over standard.
No charge to make a request. Just remember it is only a request.
The preferred locations are all of Trinidad North and Martinique 24, 25, 26. If you don't want to pay for preferred, there are pleny of locations that are not preferred but are under 5 minutes to OPR and the Main Pool. Those are Martinique 21, 22, 23, Aruba 51 and Jamaica 45.
I have never stayed in Martinique, but I can't imagine there being a good view of Illuminations from your room. There may be a few rooms in the Waterview category that could get a view. But it's $25 per night more for a Waterview. We love to watch Illuminations from the beach at Tinidad North, the beach at Martinique or the bridge.
Here's a map if you haven't seen one yet.
http://www.wdwinfo.com/resortmaps/cbrmap.htm
We love the Jamaica 45 location,.