Hi ladies!
*For the 3 year old, I'm wondering if she's not a bit more tired than normal right now. Did she recently start preschool or change rooms at a daycare? I'll tell you one thing I've learned about my son in these toddler/preschool years is that either developmental milestones or changes in activity level can really change how sleepy he is. We've had to reduce A time for a few months and then they've increased again. I'm thinking you might want to try a longer nap again and see how that works. If she's waking at 6:15 and going down for a nap at 11:30-12 that means she doesn't really have much A time in her for her age! Most LOs this age are doing closer to 6-6.5 hours A time and she's doing 5-5.5, which is what we generally see closer to age 2. I'm also thinking that reducing the nap worked at first but perhaps either she became cumulatively OT ro else something changed -- developmentally or situationally.
Anyway, I'd try letting her nap fully again and then give bedtime 5 hours post nap and see if that helps! She's only getting about 10 hours nighttime sleep now, which is 90% of the time a sign that a child is OT at bedtime.
If allowing her to nap more than an hour backfires, then you can of course experiment with eliminating the nap. but from some fo the things you've said I think you've got a child who still really needs/wants that nap and may just need more nap for whatever reason. I know there will be several moms of 3 yr olds who will reply and say that eliminating the nap made things better fo rthem.
And that may be the case! I just have this feeling in your case a bit more nap might help. But use your instincts! If you think I'm nuts, go ahead and cut out the nap and see where that gets you.
*Now, for the 29 month old I think the situation may be different. If she will sleep up to 3 hours for her nap she sounds like a sleepy bub. But if she wakes at 3 pm and then you put her down for bedtime at 7 pm she's definitely going to fight it because it's not enough A time. It may be that she's ready to stretch the amt of time between nap and bed. I think I'd at least give her 5 hours before bed, try that for 3 days, and then try 5.5 hours post nap before bed. You can also limit nap to 2 hours so that it's not robbing her of nighttime sleep.
The thing about toddlers who can sleep 3 hours for a nap is that they tend to be on the sleepier side, so you have to really be careful to honor A times. You need to offer enough time between nap and bedtime, but not too much or you enter OT land.
The 27-29 month age group often shows sleep troubles. It's usually b/c they're ready to increase A time. It's possible when you tried a later bedtime before it was either too late or not late enough. So be scientific about it. Start with 5 hours post nap and work up until you stop having bedtime issues.
For both toddlers you can use Reward Charts to get some better behavior out of them, even if they're not ready to sleep. RCs are a fabulous tool at this age because most toddlers would sell their parents for a sticker.
So, tell your child that if they are quiet at bedtime and don't make mommy/daddy come back in their room they get a sticker in the morning. Show them the stickers. Then, when they earn 2-3 stickers (you decide) they get a bigger prize -- a balloon, trip to the park, picnic in the living room, tea party, etc. Whatever you think will float their boat. For my son a Matchbox car does the trick. So we're talking something inexpensive but fun. At this age I think it's perfectly fine to tell your child they can sit and look at books until they're sleepy. If their nightlight isn't bright enough, you can give them a child-sized flashlight to use. This is actually a powerful tool too because now THEY are in charge of when they sleep. You're both seeing 60-90 minutes of protesting, so it's not like we're going from a child who falls right to sleep to encouraging them to stay up at night! They're both struggling, so lets give them something constructive AND QUIET (LOL!) to do so that you don't have to be there with them while they fall asleep.
Hopefully with some experimentation with the routine this will go away.