At 27, you're not old!
I can understand why people get caught up in the age-ist attitudes of the adcoms, but so long as you're under 30, you should be fine for all schools (and for HBS, it's 28 or under). Once you get beyond that threshold, age does become more of an issue, but other than HBS or Stanford it's not fatal.
Another thing: adcoms will cut you slack on the GPA. Everyone knows that engineering programs grade on a much harsher curve. So long as it's above 3, it's not really an issue. And the fact that your GMAT is so strong will certainly help. If you have time to do some extension classes to build an alternate transcript that's great -- but I don't think it's necessary for you. You graduated from a top 5 engineering program and you have a strong GMAT -- most people can reasonably assume that academically you're not slouch; you just went to a f*cking hard engineering program, that's all.
As for consultants being a dime a dozen - that's true. However, for many b-schools, consultants are their bread and butter; there are tons of them in b-school, because moreso than any other background, they are the most employable across the widest range of industries and job functions. Especially in this day and age, it's certainly better for the b-school admissions process than being a dime-a-dozen banker.
For the schools you mentioned, you should have a reasonable shot of getting into a few of them. Obviously HBS and Wharton are stretches (as they would be for just about anybody), but you have enough of a shot that they're both worth applying to. The other schools you should be in the mix.