yes they are all right. u can say '해피 발렌타인 데이' or '즐거운 발렌타인데이'. either way is fine. and also u can say '발렌타인데이 즐겁게 보내(have a merry valentine day or 발렌타인데이 재밌게 보내 have fun in valentine day or 발렌타인데이 잘보내 have a great time in valentine day' if I add a bit more, in korea, valentine day is a bit different just like Japan. in valentine day, usually girls do give guys gift or sweets with confession or with their heart. and March 14th, which is White day we say, guys do for girls same. and we do have lots of day such as black day블랙 데이(자장면 데이), rose 로즈 데이, pepero빼빼로 데이 and so on. but it's all added up from valentine day cuz of commercial reasons such as the White day. valentine day=chocolate day but still u can give whatever. white day=candy day but still u can give whatever. hope it can be the help. :)

Correct!! 해피 발렌타인데이~~

yes you can say 해피 발렌타인 데이 or 행복한 발렌타인 데이..or 즐거운 발렌타인 데이^^