congratulations on your upcoming baby and great job tandeming!
just give yourself plenty of time to adjust to nursing three when the baby gets here. your not just nursing 2 at once, you are actually juggling!
eventually the older ones will taper down (don't forget that when that mama milk comes in they up their intake) and you'll find your groove so it does work. it'll be an intense few months (4mos for me), but i think very worth it! i told myself to get through one year, and i far surpassed that. by the time i got to 6 months it was all routine
the best advice i got....get an egg timer. that way when you get a bottleneck (when all three need to nurse at once....those will happen) the older ones can take turns and the egg timer or even an hour glass helps them wait their turn.
when i jumped to three, my nursling were almost 4 and 31 mos. a little bit older than yours. but it worked out, and they were very good at making sure the baby got her fill.
my favorite nursing position at the time was laying on the bed, nursing the older ones while the baby sat in my lap leaning against my leg looking at me and grabbing the boys heads. very peaceful until she got old enough to realize if she wasn't nursing and they were she wanted to nurse even if she just got done.
i really love the bonds between my children, and i really believe nursing has played a huge roll. so far, each nursling has been paired up with each other sibling
there's a triandem thread and i'll go get the link for you.https://www.mothering.com/discussions...d.php?t=471380