Re: Quranic education
Saadia, my older daughter who is now 6, started her formal arabic/yasarnal Qur'an instruction at almost 5. Some people do start early but that's when I started and she should be starting 30th para in a couple of months, inshaAllah. I take her to our local masjid where they have arabic/Qur'an with tajweed lessons along with TaleemulHaq and Adaab/Akhalq, Hadees, Hifz, etc. But because the Qur'an is being taught with proper tajweed rules they are taking more time which is fine with me because her foundation and recitation will be strong.
My little one who just turned 3, has already learned the entire Arabic alphabet as she's been getting motivated by her older sister.
SO your 4, almost 5 year old is at a perfect age.
Regarding online instruction, I just met a friend last weekend who's son is also in a similar online program and she is quite satisfied with it. However, she does miss the association part and the overall "mahol" so if you have the opportunity, I would recommend you try to find a local program, otherwise, this should be great as well.