I am making this cake today for my mothers birthday. It has to travel for about 2 hrs in the car.
I am going to put a triangle board under the top piece with bubble tea straws underneath and then a dowel all the way thru. Will this be good enough to hold it together for the ride.
should be so long as you drive carefully.
of course you could take as two separate parts and finish stacking there and only have to add the bottom border on the top piece.
I don't like unnecessary risks, so I'd travel with it separated and then assemble on site. It's a simple border so it wouldn't take you long to finish it when you get there. If it were a round/square tier, I would use SPS and not worry about traveling with it assembled, but I'm not so confident about bubble straws making the ride.