Based on my limited knowledge and only for my area (management/ob/strategy):
Wharton does admit some older applicants (even 35+). May be not many of them.
MIT - not sure.
Cornell - I agree with your other source. Cornell hires very few applicants (mostly just 1 every year) and they do tend to be around 25-26.
Other good schools less biased against older applicants (assuming extensive work ex) - HBS; Duke; UC Berkeley; UC Irvine; Purdue; UT Austin; UW Foster; UW Madison.
All the best!