The beach is a great day out, our niece and nephew love it, running about, hunting for crabs and making sand castles keeps them amused for hours. I like wondering along the shoreline hunting for shells or pieces of driftwood to use in the house or garden. I have also been known to collect bag-fulls of seaweed for the garden. It makes a great addition to the compost heap, or you can use it to mulch around plants while it slowly releases nutrients back into the soil. Again, collecting seaweed is that it is totally free and great for the garden.
Best of all, a trip to the beach can feel like you've been transported to somewhere completely different and far flung, but it's completely free.