Gifts of service are rather difficult to wrap. Some have given coupons good for some act they will perform on demand, but this somewhat clashed with what the acts of service woman hungers for. Acts of service stand out when they are unexpected, not suggested, and not things that you would do anyway.
One way to do acts of service as a gift is to help your bride with certain Christmas tasks that have usually fallen to her. Help her with the shopping and wrapping. Take the kids shopping. Take the kids off her hands so she can go shopping.
There will also be plenty of tasks on Christmas day – especially if you have younger kids. Keep your eyes open, and be quick to do things. I assure you an acts of service gal will notice.
You can find fill and print coupons here.