Your children and babies are perhaps too small yet to be playing on their own, away from your immediate care, so you may not have broached the subject of 'stranger danger' with them. However, even whilst making sandcastles or paddling with you, there are important safety issues they need to be protected from: the sun's rays, for a start.
Suncare for babies and children
Across the ThinkBaby site, there are useful articles to help make your trips out with your baby or toddler safer:
Keep safe in the heat
Babies and hot weather
Staying safe in the sun
Babies, children and bee stings
Baby skincare in swimming pools and the sea
It's easy to forget, until you get there, that you are usually sitting in an exposed area when spending a day at the beach. Unless there are some exotic trees to bask under, it's a good idea to take an umbrella or one of the many UV-protective pop-up tents on the market, at least for respite for baby naps or lunch time, so that your children are not in the sun for the whole day.
Millets do a great range of tents and beach canopies from about £10. Some children's play tents (castles, tipis etc) can make useful beach shelters too, if they are made from UV-protective fabric.
Most high street stores stocking children's clothes will now offer a range of UV-protective beachwear for babies and children, including hats which shield the face and neck, and light-fabric swimming outfits which cover their bodies and dry easily while your child is still wearing them, making them bright, funky and comfortable for a day of sea and sand. A good place to look online, is www.simplybeach.com to get an idea of what's available.
Remember that a baby's skin is too thin to be exposed to any direct sun and complete shade is better than using sun blocks on under-ones. Also, avoid being out in the sun for extended periods during the brightest time of the day (even on cloudy days) - 11am to 3pm - whatever age you are.