What should I teach my little siblings (ages 10-13) from the deen? We are Muslims but I don’t want them to grow up as a cultural muslim like I did when I was their age.

Let them memorize the Quran and the Sunnah, and attend the gatherings of the people of Ilm, the scholars. Let them attend the gatherings and watch the videos, especially on topics that are simple for them regarding Tawheed, staying away from bidah, and so on, as well as the important lessons for every Muslim: some fiqh issues regarding Wudu, Salah, and so on. This type of interaction can build up character. Having friends who are on the same path, always praying at the masjid, and attending some of these lessons and halaqat together can strengthen that identity within them.