开开心心 + 地 + Verb
The adjective 开开心心 (kāikāixīnxīn) is the reduplicated form of 开心 (happy), used to emphasize a joyful and cheerful manner. It is commonly placed before 地 to modify a verb, describing how an action is performed. For example, 开开心心地吃 means "to eat happily."
孩子们开开心心地跑回了家。
Háizimen kāikāixīnxīn de pǎohuí le jiā.
The children happily ran back home.
我们一家人开开心心地过了个年。
Wǒmen yì jiā rén kāikāixīnxīn de guò le gè nián.
Our whole family happily celebrated the New Year together.
她开开心心地收下了这份礼物。
Tā kāikāixīnxīn de shōuxià le zhè fèn lǐwù.
She happily accepted the gift.