Looking to go to a beach for 4 or 5 days of relaxation. Love Cape May, but May is not beach time. I have vacation days to burn by end of May, so where else can I go? Mid 40's couple. Love walking on beach, shelling, boutiques, yummy restaurants. Not interested in night life other than dining out. Would like someplace pretty and clean to stay. Don't like glitzy, want beachy. Sanibel? Amelia Island? Hilton Head? Outer Banks?

Ooh Amelia Island sounds like it's just what you're looking for. You will find shells as well as fossilized sharks teeth on the beach, all the beaches are public and very well kept. You'll find free parking at the beach and in the historic district. You'll find numerous LOCAL restaurants with great food in the historic district which is full of boutique shops.
Early to mid-May is when the water has warmed up enough for us wimpy Floridians to get in and play! May is a great month for climate in Amelia Island. The first weekend is a big event weekend (www.shrimpfestival.com) which is fun but hotel prices will be higher. Memorial weekend will also be higher rates, but in between you may find some deals! A few hotels to consider are Amelia Hotel at the Beach (right across from the beach and comparable to a Hampton Inn or Courtyard), Hampton Inn (there are 2 on the island) or if you want a 5-star property there's the Ritz Carlton Amelia Island.
Other activities include Eagan's Creek Greenway (walking trail great for nature watching), Fort Clinch State Park, Amelia Island Museum of History, or you can book a horseback ride on the beach!

I am also an Amelia Island fan but are you driving ot flying ? The Carolina beaches will be just fine that time of year.

Amelia or Sanibel would fit your criteria.

We love Hilton Head and go there several weeks out of the year. There are many great restaurants and our favorite activity is riding bikes-the bike rentals are really reasonable. The beach is wonderful for walking.

I think Sanibel is the place, the water should be warm enough and the shelling is amazing.

Sanibel's water will be much, much warmer than Amelia Island. If that is your deciding factor. The Gulf coast is always warmer.

I would be hesitant to stay north of Hilton Head in May to guaranty good beach weather. HHI isn't even a guaranty - we spent a very cold, rainy and windy week there last May. It was rare, but it happened.