By virtue of this claim being used as a hiring incentive, can they be
forced to make the promised contributions?
The decision would be based on the prima facie elements of promissory estoppel, which are:
(1) [a] promise which (2) the promisor should reasonably expect to
cause the promisee to change his position and (3) which does cause the
promisee to change his position (4) justifiably relying upon the
promise, in such a manner that (5) injustice can be avoided only by
enforcement of the promise.
(See Havens v. C & D Plastics, Inc., 124 Wn.2d 158, 171-172 (1994)).
The difficulty lies in establishing elements (4) and (5), since the plaintiffs/employees would need to persuade the court that the notion of injustice in element (5) may also refer to the detriment of third-parties rather than referring exclusively to a detriment of the promisees themselves. Thus, the question for a court would be: Is the alleged injustice as per (5) sufficiently attached to the employees' reliance as per (4) to merit the injunctive relief?
Can a claim for essentially unpaid wages (since lower wages we're
accepted based on their promise) be made on behalf of the entire class
of employees recruited past and present based on this lie?
Yes, provided that the employee(s) can prove that the promise of charitable contributions persuaded the employee(s) to accept lower wages. I believe that proving this would be difficult because such level of detail of an employee's mind is hardly ever reflected in an employment contract or related records.