4. The children ... (to have) a good time in the park yesterday. They ... (to give) small pieces of bread to the ducks. Then they ... (to take) pictures of themselves.

4. The children had a good time in the park yesterday. They gave small pieces of bread to the ducks. Then they took pictures of themselves.

В четвертом предложении нужно использовать Past Simple, так как действие произошло в прошлом (yesterday). Форма глагола "to have" в Past Simple - had, форма глагола "to give" - gave, а форма глагола "to take" - took.

Ответ: The children had a good time in the park yesterday. They gave small pieces of bread to the ducks. Then they took pictures of themselves.