Hi T.,
My five year old daughter has a head of insane curls and it has taken me a really long time to find the right products for her, so I am happy to share what has worked for us. The very best shampoo that I have found is "NoPoo" by Devachan. Devachan is a salon that specializes in curly hair but you can buy their products on line. You only need to wash her hair about once a week. I know that sometimes toddlers get food in their hair and there is the tendency to want to clean it as much as possible, but curly hair tends to be really dry, and less is more. This shampoo doesn't "foam" up like regular ones, but feels like a conditioner on the hair. However, it cleans the hair beautifully and leaves it silky and soft. If you feel after trying this, you need a little more "cleaning power" they also have a "low poo" version. I would first try the Nopoo.
I use Jason conditioner every night and leave it in my daughters hair and comb it through with a wide tooth tortoise comb to get the knots out. Invest in a good quality comb. The cheap plastic combs can break the hair. Never, ever brush her hair! If you can get away with "finger combing", even better, but only use a comb on wet hair–never dry. The Devachan conditioners are amazing,too, but my daughter has a lot of hair and it tends to get expensive, so the Jason brand conditioners (found at health food stores and maybe specialty drug stores) have been a good alternative. To help avoid the frizzies, wet the hair every morning or night when you bathe her and apply the conditioner. Gently squeeze the water out of the hair. Be careful not to twist or rub with a towel.
Finally, for night, I found a satin pillowcase which I have her sleep on. The hair "slides" on it and won't knot as much. I know that this all sounds crazy and very "princess-like", but as she gets older and her hair grows in thicker, you will be grateful to have a "system" in place. Also, neither my husband nor I have curly hair, so this has all been a learning experience for us, trying every product on the market to see what works, plus a LOT of advice.
Good luck to you. I hope this helps!