Leave them in space
I debated about responding to this, but the comments are more innocent than the normal sort of affair suggesting technical impossibilities, so I'll bite.
The 1st and foremost problem is the fuel cells. One of the most recent examples of throwing good money after bad is a MANY $$$$$$$$$ "upgrade" to power the shuttle systems from the ISS solar power. This saves USING the fuel cells and extends the time a shuttle can spend at the station. However, it is not possible to prevent the fuel cells from leaking.
1) Once cells are fueled on the pad the shuttle must launch within 5 days or a day off is taken to top off tanks, most notably the fuel cells.
2) On a related note the US lost Skylab - an arguably more capable platform than ISS - because the last Apollo mission was left up too long and NASA was afraid this same leakage, this time of SM propellant, would prevent Apollo from BOTH raising the orbit of skylab AND successfully de-orbiting.
3) I beleive propellant leak down is also why the Soyuz capsules can only stay at ISS for 6 months.)
Back to our story, without fuel cells the shuttle has no electrical power at all and is a big ceramic meteor. NEXT as was pointed out is the OMS engines. The 2 small(ish 10K lbs thrust) restartable engines in the pods at the rear. These are used for circularizing the initial orbit, raising ISS, and de-orbit burns. WAY back in the 70s plans were for expansion tanks of OMS fuel in the cargo bay. Back then the shuttle was planned to stay up a month or more and drive around all over orbit. Sadly one thing people don't realize is changing an orbit is GHASTLY expensive in fuel and from a practical perspective cannot be done.
OMS (ironically named Orbital Maneuvering System - even though we just showed they in fact can't really maneuver at all) fuel reserves are virtually non-existent and there is no possibility to refuel. RCS (reaction control system - steering) fuel, while not as dire as OMS supply is also VERY limited.
The above I am certain of. Another area of concern is the APUs which perform adequately at providing hydraulic power for the areosurfaces in the atmosphere. However they are at their design limit there and it seems certain fuel leakage or just plain old entropy would be a problem in short order. There were also problems with coolant lines freezing when they did start powering down to run off ISS power. This may be solved, or it may not. I don't know. But it became clear you can't just hit the big red button and turn it on in a few months / years later.
As far as the moon goes, the shuttle lacks by MANY times the amount of fuel (read delta-V) to escape earth orbit. If it did so, it then would lack the fuel needed for Lunar orbit insertion. The result would be a quite unsatisfactory sling shot into deep space.
There are MANY other problems far too serious and numerous to list here, but basically building a new ship would be orders of magnitude cheaper than trying to lift a shuttle out of earth orbit.