Happy Father's Day Cipher Key

"Dear Father: Crack the cipher before you get the greetings. Love, Smart-ass Kid. "

Below is a Father's Day letter I wrote when I was nine years old. It was in a brown envelope with a Scrooge McDuck sticker for a stamp. Evidently little has changed over the last 21 years as far as the author's general frame of mind and abundant geek idiosyncrasies go.

No idea what the symbols stand for. I used to ink up all sorts of weird symbols and mandalas.

HELSINKI 7.11.1989

Hello Father!  I'm doing well in school, and today I'm writing to you, as I'm sure you already notice. How are you doing there at home? (Like I didn't already know.) Solve this puzzle for starters! Solution at the bottom right corner. Below is the code cipher key.

    5    10    15    20    25   29 
ABCDE FGHIJ KLMNO PQRST UVWXY ZÅÄÖ

8 25 22 28 28 9 19 28 14 16 28 9 21 2x28 ! ! !

Love, Oskari

[Answer: Happy Father's Day!!!!]