If i where to write this in welsh in a card is it correct.?

My written cymraeg is terrible, but I can tell you that "dw" and "i" should be should be separated. (The pronoun and "yn" can make a valid contraction, like "Dw i'n siarad cymraeg.") However, this seems like a very colloquial note, so I don't think it makes too huge a difference. Also, you have a gog dialect and mine's totally southern (Pembroke).