Transfers 2'-(5-triphosphoribosyl)-3'-dephosphocoenzyme-A to the apo-[acyl-carrier-protein] of the malonate decarboxylase to yield holo-[acyl-carrier-protein]. 2'-(5''-triphospho-alpha-D-ribosyl)-3'-dephospho-CoA + apo-[malonate decarboxylase ACP] = diphosphate + holo-[malonate decarboxylase ACP] Belongs to the MdcG family.