hey there,
Um, people know that my opinions of the admissions consultants aren't that high, especially the ones who tell you "you have no chance" just so they can get you to sign up and work with them. Ok, rant over.

You have a pretty strong profile! To answer your question, you are NOT too old for the schools you listed. Right now only Harvard and Stanford are known to go younger, and the rest still have average ages of 27-28. If it helps, I'm 31, have an engineering masters, worked 5 years as an engineer and only decided to get an MBA after working 2 years in business development. So if you can tell your story of WHY you wanted to switch to marketing from engineering, HOW you did it, and WHY that prompted you to get an MBA (if you're already in marketing, why do you need an MBA? That sort of questions), then you should have a good chance.
Your EC leadership is great, your GPA is fine, your GMAT will NEED to be above 700 (to make you competitive), preferably 720+ for the schools you're looking at. The one weakness I see is that you didn't list any MAJOR work leadership experience. You've done some good work, but if you can talk about the leadership and teamwork aspects of those jobs in your essays, then you can mitigate the issue.
DO NOT be negative. You need to get a good GMAT score. Once you do, it'll depend solely on your essays. Also, DON'T let the consultants get you down. I'd trust people on GMATClub much more than those consultants, who told me most of the schools I've applied to were "unlikely" for me.
Anyway, my 2 cents, take it with a grain of salt though.

Wharton - reach, this will be a very tough one, but age will not be a factor there
Kellogg - smaller reach, depends on great essays and how well you convey your leadership/teamwork characteristics
Yale SOM - Tough just because the class size is so small, but on target.
Tuck - Tough, but doable.
MIT - small reach, emphasize your marketing background and how you're NOT a typical engineer
Haas - Tough because of the acceptance rates, but very doable with your stats and with good essays.
Have you considered any "safety" schools? Like Michigan, UCLA, or Duke for Marketing?