You must visit the Sanibel website--even has shells one might find.
http://www.sanibelcaptiva.org/

I would suggest going by the police station and getting a map with all the
parking lots that are available for the .75 an hour fee.  For $35 you might
even get a parking decal for some of the beach access points.  If you are
spending much time there it would be worth it.  Then you don't have to keep
going back to the car and feed the meter.  I think you can still do that.  I
didn't look at the website that close but you can probably email them and
ask.

Periwinkle Park is a nice campground. .  Even if you do not camp there it is
a must to visit.  Just park at the gate and tell them you want to see the
birds and animals.

It is difficult to tell one where to shell on Sanibel.  One year it will be
better at one part of the island and the next year another.  Last winter the
best shelling was at Tarpon Bay and the year before it was at Algiers (Old
City Park).  The same for wentletraps--one year there may be more at the
lighthouse and last year they were abundant between the Sundial and Algiers.
Didn't find that our til the week before we left.    The year before there
were more between Algiers and Tarpon Bay.
Don't hesitate to ask people on the beach that look like shellers.  They are
almost always ready to share where the best shelling is.

There are 26 miles of bike paths on the island.  If you can, take your
bicyle with you or rent one.    That is a good way to get around the island.

If you overhear someone saying they are going "overseas", it just means they
are going over the causeway to Ft Myers.

Ardeth Hardin