My kids are 26 mos apart, so not quite so close together, but I was given a few very good tips before my littlest one came!
One is to have something for him to do while you are nursing, a special thing, that he only gets to do at this "time". One suggestion was to have them sit next you on the couch and have him feed his baby, at the same time. He can mimic you and will probably get bored with it and go do something else. ;) The most valuable tip I ever received, was "Just a minute baby, mommy's helping (other childs name) and we'll be right there!" This of coarse, is if the baby is crying from her bed and you are helping the toddler getting a drink, going potty, tying shoes, etc. The show the toddler that they are still very important and mommy has responsibility to both children. Wow. This was awesome! Shortly after installing this tactic, my oldest would get a bit of a "oh no" look and repeat with "just a minute baby, we're coming!" lol The thought is that the baby will be fine for just a minute of fussing/crying. You'll be there to tend to her anyways, but not immediately dropping the toddlers needs to rush to her shows a great deal of respect, importance and love. The infant will not be hurt by letting her wait for a few extra seconds.
The other idea that I did, was repeatedly had the oldest touching my belly, saying "hi baby!" "love you baby" "can't wait to see you baby". This depends on your childs ability to communicate and might not be "here" yet. However, I also repeatedly told her that baby was going to come out of mommy's tummy soon! I repeated that mommy's going to need a helper, too. (She loved 'helping'!) I'd have her retrieve a diaper or burping cloth, etc. A sticker chart for a reward system might be a good idea to help with the transition, too.
We had a very easy transition in bringing our second baby home. I hope yours is as good. Good luck!