Well, Along with everyone else, I vote for starting your daughter earlier. New siblings can be a tough adjustment on their own, but it will add to your daughters stress and yours to have to deal with a new daycare and a new baby. You may even consider having her go part of the day if the daycare is open to that. I have a few kids that come to care from just 8am-noon.... Has she ever been in care before?
Having two kids is much harder than having one...I think it's exponentially harder, not just double the work. So good for you if you can have your daughter in care that she likes where she can have a stimulating environment and meet friends her age while you give the baby and yourself the time you will need.
As far as the transition, there are some good books out there about being a big sister. Try to keep your daughter involved in helping with the baby and helping you with thing that the baby is too little to do... Kids love to feel important and values by being helpful. Remember that she will probably regress a bit and become more needy of your attention at times too, and give her what she needs. My daughter had short periods when she wanted to be held like a baby and cuddled like a baby. I'm not saying that I did everything perfectly, but we have very little sibling jealousy I think as a result of always trying to be fair and consistent and meet the needs of both kids.
I just noticed that you already have 2 little ones... in that case, I would be ready for the 5 year old to have some feelings about the new baby too!! If you can arrange it with your husband, you might consider planning some special outing for the 5 and 19 mo old so they remember how special they are and don't get lost in the busyness that happens with a new little one!!
Good Luck!!!
Good luck!!