Gluten-free cake decoration - help please

[Catz]

I wasn't sure whether to post this in recipes or here but I hope that some of you may be able to help me.

I have a little girl coming to DDs birthday party who cannot have gluten (don't know more that that e.g. how serious but am obviously being as careful as possible). I'm making DDs birthday cake using a standard recipe and have bought an individual plain gluten-free cake for the little girl. I was hoping to decorate it so it is a mini version of the main cake. To decorate the main cake (which is a character cake) I'm using chocolate butter icing, marzipan, choc buttons, white chocolate, food colouring and ice-cream cones. Are any of those things OK/out? I'm guessing the ice-cream cones are no good but I'm not sure about the rest, there's no info on the packets.

Many thanks for any help.

Could you tell me the brands of the marzipan etc, and I can check them for you ?

That's very kind of you, many thanks. Sorry there is a bit of a long list!
I have:
White marzipan - Sainsbury's
milk choc buttons - Sainsbury's (which actually do say OK for coeliacs)
Beligian White Choc - Sainsbury's
Ice-cream cornets - Askley's (pretty sure not OK)
icing-sugar - Silver spoon (I also have some Tate &Lyle if one OK one not).
Red, black and green food colouring - Dr Oetker
unsalted butter - country life.

Many thanks again for your help.

White marzipan - Sainsbury's OK
milk choc buttons - Sainsbury's (which actually do say OK for coeliacs) OK

Ice-cream cornets - Askley's (pretty sure not OK)
icing-sugar - Silver spoon (I also have some Tate &Lyle if one OK one not). OK
Red, black and green food colouring - Dr Oetker OK
unsalted butter - country life. OK

Beligian White Choc - Sainsbury's - which one exactly ? Their cooking and blue packet one both seem to have cross contamination statements

And the cones aren't gf

That's great, many thanks I didn't expect to get such specific information.

The white choc is probably the cooking one. I picked it up in the cooking aisle though it doesn't say 'cooking' on it. It is in a yellow packet. Are there any white chocs that are any good?

Thanks again for your time and help

Green and Blacks is OK, or you could just melt the white buttons and use them if thats easier

Many thanks, all done now so hope she enjoys it.
Thanks for your fantastic help.

How lovely of you to go to so much effort!!!!