I think the OP really wants to get out of the country, but with all the Ithaca discussion will also throw out Ghent (being a college town). I had to spend a few weeks there a decade ago when my mother in-law had surgery. Our oldest son was 2.5 then so we had the stroller -- Ghent was really easy to get around and very nice overall. I would assume a little more affordable compared to a larger city like Amsterdam. You can even get out to the beach (Ostend) with a 40 min train ride (great promenade and walking area) and certainly good connectivity for other weekend trips.
We were there during this large 10 day festival held in July -
Gentse Feesten . I think they have a lot of other cultural events during the summer as well.
June average high of 70 low of 55 with 9 days of rain.