Welfleet is a great harbor, the inner harbor is small, but there is SO much area just 15min away by boat to fish and explore. The ramp fee is 10$ per launch, and with a 19 and a 4wd truck you should be able to launch at low tide! Be careful there are a TON of shallow bars to get hung up on.
http://maps.google.com/maps?hl=en&q=...-8&sa=N&tab=wl
Jermeys point is a great place to have lunch and hang out, plenty of protected water to swim. The fish routinely get pushed up to the outside of the sandbar, makes for some FUN times casting on the bars.