Protein shakes and baby food sound like a good start. For a quick solution I would add powerade or similar as they also contain electrolytes on top of all the sugar and they certainly help me. I find them generally disgusting so it's a last resort for me, which is probably what they should be, yuck!
Longer term though I would ask your Gastro about getting liquid food prescribed, I've forgotten any brand names now but Nutricia do an extensive range, some of which are palatable. I had them in hospital as they couldn't provide me with anything I could digest other than Jello....