I agree with mommy-medic, even though these guys were harsh, it is all true.
As far as answering your question,
Baskets and blankets are good for posing the newborn. Make sure you provide support where needed. You'll need 3-4 blankets, as I usually roll some to create the initial support, then use the others to cover and fill where necessary. Don't be afraid to change it up if something isn't working. It's not worth fighting for, especially since your window of cooperation is going to be so small with this age group (both of them). For the 1 year old, stools are good. They like to sit on things. Definitely have their feet touching the floor firmly at all times. In fact, if they are not walking yet, don't use the stool. You will need to focus on using distractions, and then having to compete with these distractions to get in-camera eye direction.
Posing the two together definitely will be HARD. An easy shot together is to see if older sibling will give the baby a kiss. Be ready, sometimes it's quick, sometimes they'll grab the baby with "love" but will upset the baby and then you're pretty much done. Obviously, you would not have the one year old hold the baby, but perhaps using the basket, pose the toddler nearby. The more interaction you can get the better, but with an infant and one year old, it's not likely you'll get much. The one year old is still essentially a baby themselves. Don't expect much and, again, don't fight too hard for anything. If it's not working, move on! Otherwise, it's a bunch of stress for everyone for no reward.
Please do go about this carefully. Infant and child photography is nothing to dipsy-doodle around with when you're just starting out. So much can go wrong. Make sure mom understands that she needs to be nearby the entire time and she is responsible for helping keep everyone safe.