The dowels are just fine in a travel cage. Don't even worry about it.
The issue with dowels is when they are the ONLY perch a bird ever stands on for decades. Their feet need varied size and texture on perches over the long term to help prevent developing early arthritis. Sitting on a dowel every couple months is not going to do any damage. You can use a rope perch if he will be traveling overnight with you, as it will probably be more comfortable.
As for balance- Kiwi's travel cage has a dowel perch. He has never had issues balancing in the car as he just grips the perch with one foot and the bars of the cage with other. Never once has he fallen or even lost balance. Then again, I think Kiwi might have gecko feet. His play tree is plastic and got horrid reviews online because peoples birds would slip off it. He runs around, hangs upside down, swings off it with ease, so he may just be good with gripping stuff. I have heard of some birds who have rather poor balance naturally, so if your bird has trouble gripping his regular perches, vet wrap may not be a bad idea.
