As a mother who has nursed a few babies in her day, the first thought that occurred was--- that's a really awkward, uncomfortable position to be nursing from, for both the mama and the baby.
You want both to be in as natural/comfortable a position as possible, so that the nursing experience can last as long as it needs to, rather than stopping because one of them can't hold the pose any longer, or the baby can't get a good latch because they keep falling off.
Don't dogs/cats/pigs have a more reclining stance for nursing their young? As time goes on and the litter grows, they can develop into more of a horse or cow position from which to nurse--- they kindly stand still, and the babies find a teat, and the mother eventually moves away when she feels like time's up.
But I would expect a good number of your readers to have seen a nursing dog or cat in real life, or in pictures, or on YouTube... and the idea of something as strong and powerful as a wolf laying on her back with her feet in the air while her babies have a snack is going to be a little clumsy and incongruous.
Wordwise, rather than "were suckling", I'd go with something more like "suckled greedily." I haven't been around nursing dogs/wolves, but human babies will usually have a degree of enthusiasm and/or desperation in their approach to nursing which is very gratifying to the mama, and encourages them to stay still longer than they might otherwise be inclined to.