Talking to the other mom.

I wanted to message my step sons mom to ask her if we could buy a few outfits for my step son since he starts school this year and what sizes he’s in right now. But I literally have the worst social anxiety, I’ve never messaged her or texted her, I’ve talked to her a few times in person but that was it, I have nothing wrong with her I’m just a shy person and I’m legitimately afraid to just go out and message people. How would you word it?