My "shoot for the stars" goal to make that work is $300,000 net income per year with at least $100,000 going towards charity. 

The first $1,000 in gains is exempt from UBIT but the additional gains are subject to UBIT which is close to 40%.The tax is reported by filing Form 990-T.To learn more about UBIT see the following. https://www.irs.gov/charities-non-profits/unrelated-business-income-tax

They will also remember that you worked with them when times were low (it wasn't charity, it literally is only a few days).  

Local charities - foster kids, veterans groups etc. how long ahead might this take to fill?

You need to sit down and decide whether you are operating a charity or a business.

Even though I currently do not have any investments in RE (prepping to change that) I am looking for a new Charity, especially those types of charities that look out for kids in third world countries.

If the building is scheduled for demo it clearly has no value (likely a money pit) so is the land donation a significant enough tax write off against your income to warrant your charity.

Start searching Facebook and the news paper and Google for charity events.

Save your philanthropy for charities you like.

Invest 10%, give 10% to charity, and spend the remaining 80% on food, drink, travel, hobbies, and unforgettable experiences.