1) Towel- This is an obvious one but the next part is not, I always bring one towel for every person and 1 extra. The reason for the extra one is have you ever been to the beach and you, your spouse, or kiddos get something in there eye? Normally the culprit is sand. After the towels have been used they are full of saltwater and sand from being used. I always keep an extra one for the sand/ocean water emergencies.
2) Sunscreen- You should never leave home without sunscreen- I understand the need to be tanned you always look thinner, prettier, etc with a tan. Have you ever come across the people who forget or don't apply sunblock properly? Lobster city or odd tan lines. Hopefully you have someone there who can help you with the trouble areas. For sunscreen there are two things you are protecting against UVA and UVB. UVA can cause premature aging of your skin and long term damaging effects on your skin. UVB is what causes the painful and dreaded sunburn. SPF stands for sun protection factor and it lets you know how long you could stay in the sun before getting burned. For example, if you normally burn after 15 minutes in the sun without sunscreen a sunscreen SPF of 15 will enable you to stay in the sun 15 times longer using the sunscreen. Of course, the time of day the sun can be more intense. I would rather be safe than sorry so I go for at the very least SPF 50. Knock on wood, I haven't had any unfortunate sunburn mishaps in a really long time using the higher SPF.
3) Plastic Bags- I like to bring a plastic bag per person which comes in handy when it is time to go to store those treasures from the beach or wet swimsuits.
4) Toys- With little ones in tow, beach toys are a necessity. I have made the mistake of remembering one bucket for 2 children, lets just say I won't do this again. I try to make sure I have enough for both boys when possible. There is always the occasion when there is one beach toy both of them want but overall I am able to avoid too conflict.
5) Food and Drinks- The reflection from the sand and the sun beating down on you can get you really hot and dehydrated. I try to bring lots of drinks and food when on the beach. Food and drinks aren't normally convenient or readily available so Be Prepared!!!!
6) Sun shade tent-If you have babies a tent really comes in handy it keeps your immobile baby protected and some of the older ones might enjoy the break from the sun as well.
7) A waterproof case- I guess my husband and I are a little paranoid but we have a waterproof box that we got at a water park which seals water out. We normally put the key and cards/money in 2 plastic ziplock sandwich bags and then put that in the waterproof box.