We also buy the older child/children small gifts when a new baby arrives. My parents did this for our family and bought my second child a beautiful drum when our third child was born(!)... needless to say, we don't do inherently noisy and/or startling things!!!
With regards to other children. Lots of love, cuddles and stories are best for the older siblings. There are good pre-birth books now for the prospective older siblings. And we like to explain that when they're born, the new baby may well be able to hold their finger in their tiny hand and may soon be able to smile at them and will think they are really special. I hated it when my first child was told she would have a little brother/sister "to play with" as this is clearly nonsense
Like mcem, I always speak to the older children first when visiting a new baby.
We don't buy unbirthday presents - it seems important to focus on the special day for the birthday girl (or boy), but we do usually buy a few token flowers each year for the "mum" as a sort-of thank you.