In Adobe ImageReady you can resize an animated Gif. (Talking like Yoda am I!)
Open the GIF. At the bottom of the window you should see the animation palette, which shows all the frames of the Gif. If not, use the menu to display the animation palette.
Click on the 1st frame at the left end of the palette. Shift-click on the last frame at the right end of the palette. This will select all the frames. Don't worry if the main editing window only shows the current frame.
From the Image menu, choose Resize image and enter the new size. When you're done, all the frames are resized simultaneously.
Save the animation with "Save Optimized" or "Save Optimized As..." It's not a bad idea to to use the 2nd option and change the name of the file. That way you can reload the original in case you bugger it up.
Good luck.