You can add custom text to an Animated Gif. This tutorial will cover the basics on getting started.
In order to add text to an animated GIF, you must first add custom text to one of your Green Screens. If necessary, please refer to this Adding Custom text to a Green Screen Photo tutorial
With this custom text created, the option will become available under the Custom Text section when creating or editing your Gif. If you're unfamiliar with how to set up a GIF watch the tutorial HERE.
Once your GIF has been created, double click on it to open its settings screen.
To associate text on a GIF frame, first highlight the frame on which you would like to include custom text on the left, THEN highlight the custom text you want from the CUSTOM TEXT field on the right. Repeat this for each frame you would like to have this text appear on.
Click OK to save your settings. Your guests will now be prompted to type in their text after choosing an animated GIF and before taking the photo.