Shareholders are pushing family-controlled Reading International to sell Cinema 1, 2 & 3 on the Upper East Side and the Union Square Theatre as locals have already made offers. But the theater/real-estate company has lofty valuation goals and wants to participate in the developments.

The mid-block Cinema 1,2 & 3 on Third Avenue across from Bloomingdale’s is just the kind of site that gets developers’ blood flowing as an 80,000-square-foot building can be created with valuable retail on the bottom floors. They have already received proposals valuing it between $40 million and $45 million.

Reading thinks that if it is rolled into the neighboring properties that wrap around it to the north, where a pizza place has the corner once occupied by Yellow Fingers, it could become a “$200 million development.”

The owner of those properties did not return our call or e-mail.

Donald Zucker, who developed the condo next door at 205 E. 59th St. that wraps onto Third Avenue, was in the mix but pulled out as Reading wanted $50 million for the Cinema, sources said. Zucker’s office did not return calls.

Josh Zamir’s Capstone Equities, which also declined comment, has offered $100 million for both theaters. But Reading wants to sell and then buy back in after all the approvals are in place, just like it did when it sold and then bought back a stake in Place 57 from the Clarett Group.

Reading asked for a reinvestment option of up to 25 percent of the purchase price, “but the details of the option have met with some resistance from potential buyers,” Reading admitted.

To take advantage of possible tax credits, Reading also wants to jointly redevelop the landmarked Union Square Theatre at 100 E. 17th St. that was built in 1926 and was the former Tammany Hall.

CEO James Cotter’s daughter and Reading board member Margaret Cotter produces shows there, as well as at the Orpheum and Minetta Lane Theaters that the company also owns. Her brother, James Jr., also a board member, is CEO of a California fruit packer. Both are attorneys.

Last week, Reading, which also owns land in Australia and New Zealand, had a market cap of $127.7 million.

Andrew Shapiro, president of Lawndale Capital Management, a long-time shareholder said, “Capstone’s sizable offer for these prime New York locations illustrates the substantial embedded appreciation we have always contended existed in this movie exhibitor’s numerous real estate assets.”