Omniplex vouchers are a scam

Kids got omniplex vouchers for Christmas. Tried booking online for a family, and expected the vouchers would reduce the total and any remainder on the credit card as usual. But the omniplex website refuses to allow booking unless the vouchers cover the whole cost. Ended up making three separate bookings with 2 adults on one voucher, 2 kids on another, and one more paid by card. I presume the remaining value on those vouchers is now also unusable if it's less than the price of a ticket. Moral of the story, AVOID OMNIPLEX GIFT CARDS, they are designed terribly to waste your money.