I have two children, both girls, 19 months apart. When my second daughter was born I totally panicked about how I was going to do, well, anything! It seemed overwhelming especially when the second one was just born. My mom was just very practical about her advice... she told me that women all over the world manage to get through their days with the same situation and that I was just as capable as they were so she was confident I would be just fine. At the time I didn't think it was particularly helpful in terms of advice, but it did help me knowing that of course I A. not alone in doing this.
It does help to have a "schedule" in mind. I'm not sure about the strict schedule thing, as with a newborn sometimes you just have to go with what seems right at the time. And take each moment one at a time. It is nice to have an overall plan for the day, but it helps to break it down into smaller more do-able peices. "Right now, I'm just going to worry about getting the kids up, dressed, fed, and ready for the day" and maybe even have a time in mind that you want to have all that done by. Then worry about what to do next. Over time whatever schedule you have set up will change anyway as the needs of the kids change.
Also, if you need to be somewhere at a specific time you may want to start getting ready maybe even 30 minutes before you need to leave. Make sure you have the diaper bag ready, and give yourself that extra time to do emergency diaper changes (my daughters always seemed to get dirty diapers just when I wanted to walk out the door... so frustrating when I was in a hurry). However, if you are late most people totally understand why so it isn't a huge issue.
My older daughter was not really old enough to understand what was going on. Of course she knew mommy's tummy was getting bigger and there was all this talk of a "baby", but she didn't really understand what that meant for her until her sister actually came home. And then she seemed to get really frustrated a lot when my attention had to be on the baby. She acted out the most when I was feeding the baby since I couldn't really get up and do things with her. I tried to make sure that she had a snack avaialbe to her while I was feeding the baby so she didn't feel left out that way, and then would play relaxing music and make sure she had toys and things available to her in the room I was in to play with.
I honestly don't remember much else that may be helful at this time other than a double stroller was irreplaceable in terms of usefullness, so definetly invest in one. It is even better if one seat lays back so the baby can nap while the other sits up. Also, give yourself some slack and accept that everything doesn't need to be perfect. I had to learn to let some things go, mentally speaking, and accept that maybe some housework would not get done exactly when and how I wanted it, or that sometimes you may not get everything done you had hoped to that day. Let it go. You have enough on your plate with the just the kids.
You will get through it. I used to tell people that sometimes I had to leave one of the kids crying while dealing with an issue, sometimes they were both crying, and heck, sometimes we were all crying together! There will be frustrating moments and great fun moments and many in between.
You will be tired a lot, but will get through. And I understand that boys are more active than girls so you may encounter issues I didn't have to deal with. This is an exciting time for you, congratulations on the upcoming birth. Take advantage of any opportunity you have now and later to get some rest in. I also really like the idea someone else had about having a list ready so that if someone asks what they can do you can just refer to the list.
I hope some of this is helpful for you! And I almost forgot to say that this is just momentary. It gets easier as they get older. There will be challenges but they are of a different sort. My daughters are now 4 and 5. It is a different world once they get past all that baby stuff. Enjoy the now, but know it gets easier.
J.