Best way to attach an I-chord to mittens

I have recently knitted thumbless mittens for my 11 month old daughter, and I’d like to attach an I-cord to both mittens so she won’t lose them.

What’s the best way to do so?

You could make the i-cord and when it’s done sew a mitten to each end using the same yarn, even the tail at each end to do the sewing.

You could pick up your 3-4 stitches for the icord off one mitten, knit the i-cord to length, then … either bind off and use the tail to sew it to the other mitten or somehow pick up stitches on the other mitten and bind them off w/the icord.