Hi Lisa,
Hope your pregnancy is going well, few more months to go. I have a 17 months old girl and I had another girl in december, she is 2 months old now, so I can relate with your topic. Although my oldest is younger than your almost 3 years old son, I can imagine the struggles and challenges are similar. The good thing is that your son probably, at his age, is more independent than my daughter right now, I still have to feed her, change diapers, play with her most of the time, she is not in daycare, so its really hard to attend to their demands and spend quality time with both so they are happy. One thing that helps me when my newborn is awake and I have to play with my toddler is to take the baby to the play area and pretend with my toddler that we are playing with the baby, she brings toys to her, she talks to her, even sings is really amazing how they interact with each other, you might think that a baby so small wont interact with other children but they do and in my case I can see how she likes being with her big sister.
Putting then to sleep naps at the same time its helpful so you get a little rest, I know with newborns its hard or almost impossible to have a schedule but i have manage to sometimes have them taking naps at the same time and its great. It is very important to have some time for yourself 10, 15, 20 min as much as you can, so you are fresh, you do need lots of patience with 2 little ones.
Going out helps me also a lot to pass time, I remember with my first one I was scared of going out the first months, I saw it too complicated to go out with a newborn, but now with the second one the third day after being born I was out.
In terms of jealousy I think my daughter its too young to understand that she got a baby sister, to her its more like one day she got a big doll to play with hehehe so she really likes to be around the baby she calls her because she wants to see the baby and hugs her. Like I said before i always let them interact all the time.
I guess I have talked too much I think you are going to be fine, with the second one everything is easier, at least thats my experience, you have more knowledge and confidence.
I hope to meet you in any meet up before your baby is born, I am new to this group but very much looking forward to meet other moms.
All the best,
Irene.