I would think being babies they are short enough......
Maybe you could get some shorter anchor points from a scrap yard off a different car that are suitable to be fitted
I had a similar problem when I moved the anchor point for the front harnesses. My solution was to change the end of the belt (I used clip on but you could re use the original fixed points) and acquired a pair of the adjustment plates from a local race/rally shop for about a tenner inc postage as a special order. Now belt can be shortened for my skinny son or reset to fat size for me