Because they were eager to see Avita, the kids returned to the mansion early in the morning, which meant that there was still plenty of time until the day ended.
Avita realized she couldn't stay at the mansion forever because she had so many things to do. And if she stayed here, seeing the happy family, she'd go insane sooner or later.
She didn't want to poke where it hurt, no matter how greedy and selfish she had become since meeting Miguel.
However, because she was still at the mansion and the kids were around, she decided to have some fun with them and create some lasting memories.
She had never done many activities previously because she was always too busy with school or work. Avita's life was much better now that she was self-employed and getting a mistress' allowance every week.
So, as soon as she gathered the children and their mother, she told them about her plans, and the children were anxious to go out for some fun, and Lucilla didn't stop them.