Yarn weight substitution

I am making a hooded baby sweater with a back zipper. I have made this sweater before with worsted yarn as it calls for, but I found this lovely, soft 3 weight yarn I would like to use. http://www.knitting-crochet.com/found/hooswefou.html
Can I use larger needles to use the lighter yarn? I would make a swatch for gauge first. If so any suggestions on needle size to try first?

Welcome to Knitting Help!

Babies don’t have much shape so sometimes just knitting a different size is all you need to do. Babies grow fast as well so as long as you don’t go smaller the baby will wear it at some point.

The pattern has you starting with a size 8 needle and I’d probably start with what they suggest unless you know you are a loose or tight knitter. IMO 8 is a little large for DK weight (3), but maybe that’s the way the designer chose to make the fabric or maybe she’s a tight knitter. A gauge swatch is your best bet.