I think for our family, food prep is the biggest help around here. I am ravenously hungry for about 4-6 months after my little ones are born, and it is SO HARD to prepare food for little ones (and yourself) when you're juggling a newborn and a toddler or more.
Whenever I had energy, or the newborn was sleeping and the toddler/older ones were occupied, I bulk cooked/baked and prepped food. I would roast 2 chickens, make a quadruple batch of cookies/muffins/bread, chop lots of veggies and fruit for snacking, make a big pot of beans/rice/soup, make 2-4 trays of enchiladas/lasagna, make yogurt, soak nuts/beans etc. This way I would have meat, beans and rice for a wide variety of snacks/sandwiches/dinners/soups/enchiladas. Meals were much easier to put together. Also, soup is my best friend and all my children love it. They will eat soup for breakfast, lunch and dinner. It's easy to heat, serve and eat one-handed. The home-made baked goods are good for quick healthy snacks. And the veggies/fruit are awesome for snacking without having to wash/chop/peel etc every time someone wants a snack.
My other top tips are:
-co-sleep with both/all your children for naps too. I know it's hard to do many days, but if you can make it work it is so helpful. It gets everyone into a nice groove of staying asleep for long naps.
-take a mama/baby/toddler bath or shower together when everyone is feeling stressed or cranky.
-wear the newborn as much as possible.
-get rid of as much as you can to keep your home clear and uncluttered. When you don't have the time or energy to clean, your house won't look like a bomb of toys and garbage went off.
-ask the toddler/little ones for "favors" to help the new baby or you. They love this. Ask for a baby wipe, a book, a blanket, an outfit. It makes them feel less "neglected" and instead they feel they are an important and much needed person, not just to the family, but to the new baby.
-be outside as much as possible with the new baby and toddler/little ones. It's calming for everyone.