Just going to nod in agreement about early bedtimes. my 18 month old and 3 year old go to bed at 6.
I think this is a great time for you all to build a really solid sleep routine. Take a few weeks and figure out what works for you then you'll have the whole summer to get it set.in.stone. before the baby comes. My kids know that we do XYZ every single night. We eat dinner, do chores, teeth & PJs, one song, sleep. It could be 4:30 or 10:30 and they'd fall asleep because those actions in a row = sleeping time.
I'd also encourage you, as you teach her this new routine, to have daddy heavily involved for easier transition once baby comes.