You have so many great options to choose from, however, I did the heavy lifting for you. IMHO the P45 is the lowest-cost, 88-note, weighted-keyboard digital piano that Yamaha offers. This digital piano has a basic set of features, ideal for the needs of the beginner piano student.
I’m still working on this one… Once I have found a valuable “most-bang-for-my-buck” sheet music website, I will let you know. Best if you sign up for my exclusive content signup list.
If you are seeking the best printed piano book for a child, which is specifically tailored towards a beginners mind set, come back in the near future and check out this section again. I’m currently evaluating the best picks.
I believe above model Songmics Piano Bench represents a fair mix of comfort (PU leather), convenience (sheet music storage), flexibility (adjustable height), quality (sturdy wood construction) and cost effectiveness. Most important is an adjustable height since you are purchasing for your growing child.