DH and I both got tshirts that are XL. He's maybe an L, and I'm like S/M.
I *need* to make them smaller, but I'm afraid of screwing up because they are very improtant to us.
Can someone please help me and tell me which steps I should take?
Well, cotton will shrink in high heat, but many t-shirts are pre-shrunk and won't shrink much more in the dryer. Also, if they have certain types if decorations, it's not good to put those through the dryer.
You could try running a seam from the hem of the sleeve down to the hemline, underneath the arm. They are likely to twist after washing, and for the small size, you would probably need to shorten the sleeves and the hemline as well. I would bast or pin first and try it on.
You could try cutting off the t-shirt design and sewing it to a t-shirt that fits. Or putting it on a denim jacket or a tank or something different, so it looks more purposeful.
If the design is on the back, you could change the t-shirt from a shirt to a cardigan by cutiing open the front and trimming it. Or try to think of other ways to wear it without just being a t-shirt, if that makes sense.
you sew, right? if you really want them to look nice, i wouldn't try to adjust the shirts. especially going from an XL to S/M. if it were me, i would rip the seams and use the fabric to make new tshirts using a pattern in the correct sizes.