I just spent last week in Ghent and I would recommend staying there for the balance of the trip (we spent 6 days/5 nights and to me it wasn't enough). Brussels was nice, but it had the same big city feel that every big city has. We spent our last day there due to an early flight. I think 2-3 days in Brussels would be enough for me. This was my second trip to Ghent and first to Brussels (other than just using the airport).

Ghent is centrally located in Flanders, so it's only about a 30-40 min train to either Bruges or Antwerpen. We didn't go out there, but I think it would be easier to get to Ypres as well.

We took one day trip to Bruges and Ostend. I think after going I would would split those into two separate days as I would have liked to spend some more time in both cities.

We also did a day trip to Amsterdam just as a say-we've-been-there type thing. I would probably skip this and do a dedicated trip instead. 3.5 hrs each way.

If you drive be aware that Belgium has national speed limits, so they aren't posted unless it's a special case.