Baby sweaters often have slightly shorter sleeves though because the cuffs end up in the mouth being drooled on or dragged into everything. But they can also be turned up if a little too long, so yes you can make them longer,maybe an inch or two. Same for the body length, make it an inch or two longer. Babies tend to grow in length faster than width, so a sweatrer that's slighter longer can be worn a few months longer.
sue- knitting heretic