Marion, I think the idea of singing in a language that you've studied is great, especially if some of the residents in the places you play have that as their native language.
I sing quite a few songs in German, Italian, Yiddish, Spanish, and French because those are all languages that I've either studied or languages thatI've been exposed to a lot and are related to the ones I have studied.
I also sing a lot in Hebrew, because I play at Jewish homes a lot, and the residents and staff sing with me, so I get to hear the language, too.
I learned "Ja, Vi Elsker Detta Landet" because I had a regular gig at The Norse Home in Seattle. (I studied a Norwegian language book a bit and had some of the residents sing the song with me so I could hear how it sounds.)

If there are residents whose first language is something other than English, they will usually be delighted to have you try to sing in that language, even if you don't do it very well. (They can be very helpful in correcting your pronunciation, too. *G*) But, as has been said, one or two of these per visit is plenty.

Genie