If you are there for a day think you are pretty much spot on.
Maritime Museum followed by the Observatory (good views over London)
Wander back through the park and through the Naval College (take a look at the Painted Hall) which brings you out near the Cutty Sark.
Depending on when you are going and who you are with the market may be worth a look round.
Personally I’d leave out going on the Cutty Sark if its just for a day.
Boat down to the Thames barrier is good for the views through the Naval college up to the Observatory (or take the foot tunnel under the Thames) . Also good going into central London as you go past the old wharves in Wapping and Rotherhithe plus under Tower bridge.
Eating wise depends what you are after but there is a cheap noodle house by the Cutty Sark DLR or loads of pubs.