Rim height and ball size

I would like your feedback
I am conducting a developmental class for beginners ages 3 - 6 years.
The class would be half instruction half games
My plan is a 6 foot rim and and the mini ball international size 3. How many inches in diameter is this ball? I want all participants to have their own ball for drills.
I am trying to purchase balls in bulk to save on cost. A good source for youth balls?

Also...
What size rim and ball should I use for ages 7-9?
I am thinking 8 foot rim and 27.5 balls?

Appreciate your expertise feedback

Here's what I recommend:
https://www.breakthroughbasketball.com/basketballs/size-chart.html

We offer some discounts on the size 3 ball and you can also see the size info here:
https://www.breakthroughbasketball.com/store/shopexd.asp?id=128

* Team discount. Order 5 or more and get 15% discount.

8-9 foot rim is about right for 7-9 year olds. But you'll find kids that age play on 10 ft rims the majority of time in their youth leagues, etc. Not saying thats right but how it is.

Thank you for your reply.
How do I go about receiving the 15% discount?

If you add more than 5 to the shopping cart, it should now automatically add the discount. If you have any issues, let us know.