Leave the kids at home.
If you wanted to go used you could easily get a Honda Element which has tons of room for under 20k. In new cars you could look at a Nissan Versa which has a surprising amount of room for a small car.
The 2013 Honda Civic has 34.3 in. of rear head room.
The 2008 Honda Civic has 42.6 in. of front leg room.
The 2012 Honda Odyssey has 63.3 in. of rear shoulder room.
The 2009 Honda Odyssey has 64.4 in. of rear hip room.
The 2013 Honda Insight has 42.3 in. of front leg room.
The 2013 Honda Insight has 52.7 in. of front shoulder room.
The 2001 Honda Accord has 54.9 in. of front hip room.
The 2011 Honda Insight has 35.9 in. of rear head room.
The 2009 Honda Pilot has 38.5 in. of rear leg room.
The 2009 Honda Civic has 53.0 in. of front hip room.
The 2013 Honda Pilot has 56.9 in. of rear hip room.