Singing in another language is common practice for experienced singers. It's a great technique for learning language, also.
Music makes poetry memorable. With the notes, the words are easier to recall. The melody carries a sentence as it floats along, and the rhythm and rhyme harmonize in an unforgettable way that is attuned to the way our brains think.
To teach a song in a new language, I often begin by doing some speaking and repeating back of short phrases, to learn to pronounce the lyrics. Then, we sing and repeat short phrases of the song with melody, to familiarize the group with the tune and how the words fit to music. When the group seems bored, I sing the entire song or at least a first verse and refrain, so that they can see what the big picture will sound like and what our goal is. With an objective in sight, it's easier to be motivated to work towards that reward (as long as the song is one that they like and are hoping to learn.)
Practicing a little bit at a time, over a period of days or weeks, works well. Our Sunday school learned four Spanish songs in six weeks, with 10-20 minute singing sessions each week leading up to our program in church. All told, we learned 30 vocabulary words, including the lyrics to Jesus Loves Me. The children challenged themselves and grew tremendously in their respect for the sounds of another language, the concepts and expressions of another culture, and of their own ability to take on a challenge.
Here's to you and your musico-linguistic adventures this week!