My parents were not happy about me meeting him tomorrow
My parents are not allowing me to go see him tomorrow
(1) My parents were against about me meeting him tomorrow
'against' = 「反対」
(2) My parents were not happy about me meeting him tomorrow
'not happy' = 「満足ではない」のような意味として用いられ、同時に「反対である」ということを伝えられます。
(3) My parents are not allowing me to go see him tomorrow
'not allow' = 「許可しない」「反対する」
日本 
