For a family I would consider the Affinia, an all-suite hotel just off North Michigan Avenue, or the Embassy Suites which is also close to North Michigan. You get extra space and a kitchenette for the same price as a standard hotel.
For a couple like the OP was requesting - the Intercontinental is IMO the best positioned hotel in Chicago, and it's gorgeous. Right on N. Michigan. Conrad is also nice, slightly tucked in off the street.
Chicago is a great city for good, centrally located hotels, have stayed in quite a few of them over the years. The Drake (favoured by Aer Lingus crew) is my least favourite central hotel (rooms are very dated), with the Sheraton and the Intercontinental being top of the list. I also wouldn't recommend the Grand Hyatt for an older couple as it's huge and there can be a LOT of walking involved just to get to and from your room.