Is it okay to take your kitten on a trip for 3 days ???? 7 hours in a car??
Yes it is okay...BUT.
You want to get the kitten used to car travel whilst in a cage since that is the only safe way to drive with a kitten.
Buy a cage and encourage her to play in it with the cage door open. (Throw in a cat toy maybe with some catnip)
Next close the door for short periods. Stay close by so the cat feels comfortable.
Next carry the cage around the house from time to time.
Next take her in the cage in the car for short trips.
Next take her in the car for longer trips.
Do all these steps over a period of a week or 2.
NOW SHE IS READY.
You should also try putting a harness with a leash on her for short periods in the house.
At first give her attention/petting/or cat-treats to get her comfortable.
Then make the periods longer.
Then take her outside and try to walk with her for progressively longer periods.
Make sure she is comfortable...if she is not the training won't work.
I don't know what kind of trip you are planning but if you are driving for 3 days straight...the kitten will need to stretch her legs....that's why I suggest the leash/harness.
Dog owner and breeder for over 20 years