Probably a little late, but whatever the coins are stored in just make sure the seams are covered over with painters tape. This will keep the any residue from coming in through the cracks.
Acrylic is a paint that I use in homes w/ children and customers with allergies. It applys right over varnishes and oil base paints. They for the most part are a low voc paint, with a long lasting washable finish. They also dry extremely fast
Spock......listen to yourself and you're own remedies........place all in plastic bags and weather the storm
I would do both seal the cracks and but the collection itself in plastic bags. This is about the best you can do and should be safe. Paint on and Prosper...Mont.