I second Khan Academy and PBS Kids. I also recommend ABC Mouse.
It’s 6.99 a month but Pok Pok is so awesome! It’s like a Montessori method of playing fun games. He will be asking for Pok Pok trust me! And they are learning without even knowing it.
My son loves Lucas and friends! There’s so many different apps for music, drawing, and writing and they’re all free and no ads 😊
I second Lingo Kids! Or endless reader that one is great too.
We use Bebi Toddlers but are interested in something new also & more advanced but it has tons of free games and great coloring ones too. There are no ads & free trials periodically for everything but so many already are just free - tracing letters, counting, matching etc…
"My very hungry caterpillar" is cute and my 3 year old likes it.
My 3 year old loves Khan Acadamy Kids and the PBS Kids Games apps