I'm no pro, but I've brewed enough to throw out some knowledge. Your process sounds pretty solid. I actually brewed a cream ale not too long ago. Drink one and read the BJCP guidelines along with it. I though the cream ale I brewed was way off, but after reading the actual guidelines it wasn't too far off. Definitely not my kind of beer. A little too light on the flavoring, but that's what a cream ale is........I brewed it for the same reason you did(for my buddies).
Anyhow, if you are still have trouble with your heat loss....check out this video. I found a cheap but very useful way to seal all the heat in my mash tun. I can lift my cooler lid to check my mash temps and not loose a degree. It worked out better then I hoped. Good luck.
Check out this video
Aroma: Faint malt notes. A sweet, corn-like aroma and low levels of DMS are commonly found. Hop aroma low to none. Any variety of hops may be used, but neither hops nor malt dominate. Faint esters may be present in some examples, but are not required. No diacetyl.
Appearance: Pale straw to moderate gold color, although usually on the pale side. Low to medium head with medium to high carbonation. Head retention may be no better than fair due to adjunct use. Brilliant, sparkling clarity.
Flavor: Low to medium-low hop bitterness. Low to moderate maltiness and sweetness, varying with gravity and attenuation. Usually well attenuated. Neither malt nor hops prevail in the taste. A low to moderate corny flavor from corn adjuncts is commonly found, as is some DMS. Finish can vary from somewhat dry to faintly sweet from the corn, malt, and sugar. Faint fruity esters are optional. No diacetyl.
Mouthfeel: Generally light and crisp, although body can reach medium. Smooth mouthfeel with medium to high attenuation; higher attenuation levels can lend a “thirst quenching” finish. High carbonation. Higher gravity examples may exhibit a slight alcohol warmth.
Overall Impression: A clean, well-attenuated, flavorful American lawnmower beer.