RO water is fine to drink. Its the same filter systems many of the bottle water companies use. IF you attach a DI filter to the system, its pretty much said not to drink RODI water. You can run both systems fine, just split off a tap for the RO water and put a 1 way valve before the DI filter so no DI water gets back flushed into the RO side.
You can actually buy RO systems at most home improvement stores.