Can I buy a gift card for a repair as a gift for someone. Ie: my mother needs her iPad repaired and I wanted to pay for it via gift card for Christmas

Yes, you can buy an Apple Gift Card for repairs at an Apple Store.

You may be able to send in the iPad to Apple for repairs, but ask if they will accept an Apple Gift Card.

Also, be advised that the country you issue the Gift Card will have to be used in the same country - not a different country.

Gift cards are regional and you should make sure you do not buy the iTunes/App Store gift card by accident