January is perfect time and 3 weeks is a great amount of time for NZ, you will probably see more of it than i have hehe and I live here.
…you should look into staying a day or two extra at the start and end of your tour too.
Our tour had a mixture of ages, 18 up to 39.
The oldest guy (39) was having the time of his life!!
we only had a couple of people under 21 but the drinking age in the states is 21 so thats probably why. a lot were around 24 - 30 age group.
I was 35 years old on my trip, so you will honestly be fine.
USA is amazing, I cant wait to go back
Is there any travel expo’s in your area coming up?? Top deck may have a stand on display?
you can go ask them questions or they have an online chat on their website too
Honestly don’t be scared about booking it, it will be one of the best things you do! I promise!