Bill - forget the ICS300 and go for the ICS480, this will make it more versatile later on when you start to buy something that flies faster (drawing more amps), nevertheless the ICS300 is fine.

The GWS receiver works well and so do their servos. Do you really need 2,400 mAh? For that sort of a park flyer you want to keep it light, try for a 1,350 mAh or even just 1,500 mAh. The weight savings is great. Please do not go for 3S as most 370 motors will not last long with 3S.

The charger seems decent, try also to look at the Triton or Tahmazo.

As for High Discharge rates ... 5C is NOT high ... its should be 15C. 10C is just average. With EP you will need to calculate AMPS as if not you will burn your ESC or kill your batteries. Gears ratios and prop sizes are important but not that bad for your park flyer. Example:

If your set up will draw 15A then your ESC needs to handle 15A min for constant draw. This is stating the obvious. As for the battery ... if it is a 1,500mAh with a 5C rate then its NOT sufficient for the 15A as 1,500 mAh with 5C only gives you 7.5 amps draw on the battery, using this battery will kill it as the battery cannot keep up. But something like 3,000 mAh 5C can give you the 15A that you need or perhaps a 1,350 15C battery.

Li-ion batteries work fine for your park flyer but their discharge rate is generally not as high as Li-ion. I use Li-ion for my slower planes and li-poly for my higher draw planes.

No regulator required ... the ESC sorts it all out.

Some tricks ... try if you can to solder the ESC to the motor, direct and DO NOT use the connectors, this will give you more oooomph. As for your battery connectors try to use a Deans plug and not the smaller JST connectors. This will benefit you in the long run like getting the ICS480. It allows the amps to be drawn with more efficiency.