Tea

I know nothing about southern sweet tea, but here are few things I know:
If the tea leaves are broken, like in tea bags, the tea will get bitter more easily. Try getting some good quality whole leaf tea.
There is no such thing as low caffeine tea. Only less tea. Some brands/producers might make claims about the caffeine content of their tea, but as far as I know, there is no way to grow low caffeine tea.
Tea contains considerable amount of oxalates. If you or someone in your family has problems with kidney stones, you might want to keep your daily tea intake within safe limits.

One thing you might want to try is grandpa style brewing. Grandpa style brewing means, you put some tea leaves in a big mug or bottle and you keep refilling it with water as you drink from it. Many kinds of teas (green, white, black, etc.) can work for this type of brewing, but you might need to use less leaves as you would when brewing some other way.