Honestly dear I don’t want you to spend money on subscriptions. I know app engages your kids but once we make a habit they will be addicted to screen time more instead many craft works like making flower pots with colored paper, DIY activities in many YouTube channels, making of opposites from flash cards, numbers on flash cards, counting numbers with colorful pompoms, many online worksheets where kids can scribble words, I would also suggest you to make some interesting activities with your child not only to engage but also spend time with him to understand in what ways you can improve your child.