plz help me out for my mom and dads 25th anniversary

hi, i'm really confused about my mom and dads 25 th anniversary,.. its in 2 months from now but plz advice me. i'll b every grateful to u. to start with , i am 18 my elser sister 22 and my younger brother 15.. we all decided to give them a surprise but actuaaly want it to be differesnt than how we celebrated thei other anniversariees.. u know we want to be different this time. first of all, i dont know what should we give them that would be forever.. you know what i mean??
secondly, how should we arrange the party?but the problem where we actually get stuck is what should we give them so that its memorable. we dont wanna give perfumes, shirts and stuff.. we have been giving this all these years.. please advice me... thanx!