butter icing

Hello Sue and welcome.

I'm moving your post to the relevant baking forum on the site, where I am sure you will get some helpful advice.

There's a white chocolate buttercream frosting that holds up better in the heat that my baker has used. I don't know the recipe off hand,  I'm sure it's here in this forum.  If not, google it.    Best if luck!

Siduri posted this recipe for white chocolate buttercream frosting in another thread.  It was the one I was looking for and I think it would work well for your cake.

this is from Rose Beranbaum's cake bible pg. 237

enough to fill and frost two 9 inch by 1 1/2 layers or three 9-inch layers.  She has a note to reduce the butter if the cake is going to be made where it is hot

9 ounces or 255 grams good quality white chocolate

12 oz (340 gms) cream cheese softened

3/4 cup (6 oz) (23 gm) butter softened\

1 1/2 tbsp lemon juice

Put some water in the bottom of a double boiler and make sure it won;t touch the bottom of the upper part of the double boiler.  Bring to a boil.  Then break the white chocolate into  the top of adouble boiler, and take it off the heat. 

stir till melted.  put back on the heat if the water has cooled too much, but be very careful because it can burn.  It can take about ten minutes

stir till smooth

let it cool

in mixing bowl beat the cream cheese till smooth and creamy.  gradually beat in the cooled white chocolate till smoothly incorporated.  Beat in the butter and lemon juice (or vanilla, which i prefer)

If you refrigerate it bring it to room temperature and beat it again to prepare it to use for frosting a cake.  DON'T heat it though. Let it get to room temp. 

This can hold up well and can be used to decorate.  The white chocolate give it body. 

you'll need to adjust quantities to cover the wedding cake, depending on how big it is. 

this is from Rose Beranbaum's cake bible pg. 237

enough to fill and frost two 9 inch by 1 1/2 layers or three 9-inch layers.  She has a note to reduce the butter if the cake is going to be made where it is hot

9 ounces or 255 grams good quality white chocolate

12 oz (340 gms) cream cheese softened

3/4 cup (6 oz) (23 gm) butter softened\

1 1/2 tbsp lemon juice

Put some water in the bottom of a double boiler and make sure it won;t touch the bottom of the upper part of the double boiler.  Bring to a boil.  Then break the white chocolate into  the top of adouble boiler, and take it off the heat. 

stir till melted.  put back on the heat if the water has cooled too much, but be very careful because it can burn.  It can take about ten minutes

stir till smooth

let it cool

in mixing bowl beat the cream cheese till smooth and creamy.  gradually beat in the cooled white chocolate till smoothly incorporated.  Beat in the butter and lemon juice (or vanilla, which i prefer)

If you refrigerate it bring it to room temperature and beat it again to prepare it to use for frosting a cake.  DON'T heat it though. Let it get to room temp. 

This can hold up well and can be used to decorate.  The white chocolate give it body. 

you'll need to adjust quantities to cover the wedding cake, depending on how big it is. 

Any possibility of frosting the cupcakes when she gets where she's going? 

are these going in an air conditioned car?

You can also fill the cupcakes and use very little icing or dip in choco.

If you are in a large town you should have dry ice available. It's in the up scale markets here.

If you want to go dry ice, I can explain packageing.

pan