Ooh, you'll have your work cut out.
Congratulations!!! It'll be fab. I was pregnant again when DC1 was 9 months old. And then pregnant again when DC2 was 6 months old. You soon get used to managing more than one and my DCs really enjoy being similar ages.
How you manage them really depends on what they're like, my older children were all good sleepers by the time the next baby arrived so that made life easier. The only advice I'd give is that be prepared that sometimes one child will have to wait - even if they're crying/sulking/starving etc because you can't always do everything at once. As long as they get the attention they need when your hands are free again then nobody will suffer long-term effects. I promise!
Very best wishes!