Hi there,
All three of my children are still nursing. My oldest (will be 5 in October) only nurses at bedtime, and not every night. I actually thought for awhile that she had weaned (she nursed 3 times maybe over about 6 months), but she's back to every night.
My middle child (3 years old) nurses quite a lot. 6-8 times a day, I would guess.
And my baby nurses like - well, a baby who still takes very little in the way of solids!
It isn't such a big deal juggling the three of them in terms of milk supply, etc., although I do sometimes get complaints at bedtime from the last child to nurse that there is no milk left!
The biggest difficulty I have had is with my own feelings. I find that it can be very difficult for me to nurse my older two children - creepy-crawly feelings, etc., while they are nursing. Sometimes it's easier to nurse them than others.
I just try to respect my own feelings while respecting theirs. They both know that sometimes Mommy cant nurse them for long periods of time. I always warn them when it's about time to let go, and then give them to the count of 5 - there usually isn't a problem. They unlatch and that's that (until the next time!).
Perhaps not ideal, but it's allowing me to continue to nurse them, so that's what works for us.
Congrats on your pregnancy, by the way!