If Loki likes carrying things (and you fancy a risk-free day) why not just get someone close to lead him up the aisle with a basket handle in his mouth when the vicar/registrar calls for the rings? Then just ask him to sit when he reaches the 'line-up' so the person on the other end of the lead can stand face-on to him, take out the ring cushion, thank him and hand it over. If you keep him out of sight at the beginning, everyone will look towards the entrance when the movement starts and it will have a real 'Ahhhhhh' factor, particularly if Loki is wearing his posh bowtie. I think simple is best as you'll probably have enough to worry about in the hours before without having to run through your display routine while one person is attempting to paint your nails and another is trying to get the flowers in your hair.
And there will be less challenge for Loki if he gets stage-fright or wedding nerves.
Good luck and let us know all about it. It makes me go all gooey just thinking about it.