as a low level elite, i doubt you'll be getting many "bump-up" upgrades. when the economy cabin is oversold, the airlines normally start at the top of their ff status list and work their way down so the few upgrades are normally snatched by uber-elites. one way to enhance your prospects of getting bumped up (though not very reliable) would be to pick an airline that doesn't have a strong presence in the cities to which you will be flying so that there are fewer elites to compete with (i.e. don't pick ua if you are flying to-from sfo).

i think your dad has it right with his choice of aa and exec plat. with exec plat way you'd get domestic (inc. mex and caribbean) upgrades on whatever published fare you fly on as long as the space is available (and it normally is). continental offers complimentary upgrades to all elite levels but people i know routinely discuss how difficult it is to get upgraded due to the number of elites overwhelming the number of upgrade seats. a discounted ticket on co would further lower your upgrade chances.

all in all i'd suggest either co (because an occasional upgrade (for a low level elite) is better than none and you can credit your travel from dl and nw). or i would choose aa (with the goal of eventually becoming exec plat). keep in mind that with co, you will only earn 50% eqm if you are traveling on the lower coach fares you mention (incl nw and dl) so obtaining gold on co (at 50k eqm miles) could mean you'd need to fly 100k actual miles at which point you would have become exec plat on aa had you chosen them (since aa allow exec plat qualification on *either* eqm or actual miles).

if your travel continues to grow, follow in your father's wake and go for aa exec plat. i think that would be the best option to provide you with the fare flexibility and upgrade efficacy you are seeking.