This is often the hardest part of the day for a big brother or big sister, and moms are always searching for ways to help their toddler or older kids feel engaged and loved during these times. Not to mention ways to combat resentment and desperate attention-getting tactics.
Here's something you can do: put together a nursing basket for your toddler or older children to take out whenever you are nursing the baby. Just gather a few special toys - maybe even a babydoll for them to "nurse" too - and put them together in a basket that only gets to be out and played with during nursing time.
If you want, you can include some books and toys that you can join in with while you nurse, but make sure that anything you include that requires you to engage is something you are happy doing (and able to do one-handed!) while you nurse your baby at the same time.