christmas dinner

hi everyone,  im not  sure if anyone can help me out,  we normaly have prawn cocktail for starters for christmas dinner, but im not sure im my girls are allowd to eat it, we use do use prawns that have been cooked and then frozen but i don't know if they are allowd them, my girls are 15 months and 2 1/2 years, i might be worrying about nothing but if anybody can tell me if they are ok to eat them it would be much appreciated, thanx very much