Hi Irina, although not incorrect, the use of 'will' that many times is probably a bit clumsy as you point out. Perhaps a better way would be to link the sentences. Tomorrow I will go to the seaside (to go to sea would mean to sail not to the beach) and lay on a beach. The second sentence would indicate you would be returning home and bringing the lotion again. "Tomorrow I will go to the seaside and lay on the beach. I will apply sunlotion because I won't want to burn. The forecast says it's going to be very hot"

Hint: You should consider using 'going to' instead of 'will' in certain cases http://www.perfect-english-grammar.com/will-or-be-going-to.html.