Taking the child to visit in a country where the parent’s language is the language of the environment is a great idea!, it is very helpful. If it is practical: taking the child to visit other country at early age 2 to 4 years old, help them a lot in their language skills and sending the child to spend time with grandparents at about the age of eleven or twelve is also a good idea, for many reasons.
This is probably a good place to remind parents and children that a multilingual environment is also a multicultural environment, and that it is very difficult if not impossible to separate language from culture. Without a context (culture) for the language, the child will have difficulty making sense of the meanings underlying the words.
My Old daughter (5 years old) is completely bilingual English, Spanish now, she values the languages. I took her to Peru when she was 2,3 and five. I did not think too much about how she learned Spanish, everything was natural for her, she will speak Spanish to me and turn around and speak English to her Dad with not problem, but..
My youngest one she is 4 now. She went to Peru when she was one year old and she hardly remember that of course. but I have being talking in Spanish to her since always!, and she never will answer me in Spanish, she spoke English to me and everybody, she did not want to speak Spanish At All.
When she was 3 almost four years old, I thought to myself Gezzz! can not believe she does not speak Spanish at all, after all this time I have being speaking Spanish to her and putting a lot of effort into that. She understood everything I say all the time, but she couldn’t make any complete sentence at all.
So I decide to take her to Peru plus need to get some things done there as well. I stayed for a month, it took her one week to start making whole sentences. ONE WEEK! could you believe that? by the second week she was making perfect sentences and speaking Spanish fluently.
I thought SHE DID NOT KNOW how to make sentences, she did not know how to speak Spanish. I have to confess I WAS WRONG!. She had everything in her little brain, everything!, it was just she did not want to, WHY? because she did not value the language, she did not think other kids in other countries speak Spanish as well, she did not think that was an important language to learn, she did not think she need the Spanish at all.
First week kids will say to her, I can not understand you, kids will speak Spanish to her and since she understood she will speak English back and kids will say again I can not understand you, can you speak in Spanish? that was it, she want the kids to understand her, she is very relational, she want to play with the kids, have a good time with them.
My oldest daughter she is very perfectionist, she cares more about speaking right and doing things right so I may say traveling to Peru helped her a lot but more it helped her in speaking it right, like conjugations like: Yo fui, el fue, nosotros fuimos, ustedes iran.. etc. which took her a lot of time to learn until we travel to Peru she learned in one month.
But to my younger daughter traveling to Peru helped her to understand that Spanish is important too, just as important as English, in fact she will have more friends if she speak more languages, she love having friends.
I will say if you are capable to travel to other country. DO IT, do not think it twice! GO! if you are not, well groups of kids who know the other language will help a lot!