This morning my son was excited to go to athe daycare center which he goes to everyday ;) This morning my son was excited to go to the daycare center which he goes to everyday ;)

Use "the" when writing about something specific.

This morning my son was excited to go to a daycare center whichre, that he goes to everyday ;) This morning my son was excited to go to a daycare centre, that he goes to everyday ;)

Also it’s lovely weatherthe weather is lovely today. Also the weather is lovely today.

A more natural way to talk about the weather (the weather becomes the subject).

Also it’s lovely weatherthe weather is lovely today. Also the weather is lovely today.

Thoese small things made me happy :) These small things made me happy :)

I am collecting such every such small happiness and putting them softly in a treasure box in my heart. I am collecting every such small happiness and putting them softly in a treasure box in my heart.

Because you start the sentence with "I am collecting", the tense of "put" must match: "and (I am) putting"

I am collecting such every small happiness and putting them sofgently into a treasure box inside my heart. I am collecting every small happiness and putting them gently into a treasure box inside my heart.