Dear !@#$%
Riga is very nice - great choice!
Check out the latvian riflemen monument - I really like this sculpture
museum of the occupation.
if you're bored you could get the train to Moijari beach. the suburban trains are pretty good.
drink aldaris beer. eat pelmeni (actually might be estonia but they'll have similar)
I can't advise you too much because when I was there last it was 2005.
If you go to Helsinki try the ferry to Tallinn.
the Baltic countries are great.