I'm really new at this so this is my inexperienced opinion but I would try and contact them first. Since this is something that has some sentimental value to you you're not going to want to send it unless you're sure you'll get it back.

I have my son's toddler Witten Jersey that he out grew and was wanting to see if I could get it signed so I can put away for him for his 1st collection. Since its larger then a card, should I send a letter first asking with a picture of him in it? Thanks