Great job Lampada, I was about to translate that song myself, I really liked it!

A couple of things:

И хотя нам прошлого немного жаль, -- We are sorry about the past, yet
Лучшее, конечно, впереди! -- The best is probably ahead!
and even if we are a little sorry about the past,
the best is of course ahead!

К новым приключениям спешим, друзья! -- Rush to new adventures, friends!
Freinds, we are rushing to new adventures!

Ах, зачем же этот день кончается? -- Alas, the day is coming to the end!
Пусть б он тянулся целый год! -- Why not it lasts for the whole year?
Ah, why is this day ending?
Let it last for a whole year!