There are plenty of summer camps in and around Taiwan. If you want to immerse your kid in Mandarin at 5years old then the YMCA do a number of day classes and are aimed at local Taiwanese kids. My son has joined these classes (Beitou branch) and they do a range of activities - art, science, swimming, basketball - and it has improved his Mandarin considerably.
There are other summer camps but check out the parenting section in www.forumosa.com and search summer camps. If you read Chinese this site
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