The beach mussel has shown us on the North Sea very good services. They offered plenty of room for two adults and four children. Even with a moderate breeze (3-4 Bft) with the opening against the wind the guy lines were not needed. I definitely recommend is to buy sand pegs (30cm) in addition. The supplied these to be used for lawn, but not for the beach. The shell is built up relatively quickly. Due to the size of a second person is required for the construction and dismantling at a moderate breeze. After we found out the "correct" order for the threading of the rods it was particularly easy (starts with the red bar (the largest)).
