You didn't say if you wanted light, medium or dark, or pure, grey, or greenish. Three threads that might help you narrow down your choices:

Darling Baby & Toddler Rooms

Kid Room Eye Candy! Kids to Teens

Blues

Here is a link that might be useful: Main Gallery Link

BM smoke. my son's room is this color and i can't explain how much i love it. it just evokes a feeling of warmth, fun & sophistication. it looks warmer than this in person. has more of a slate w/aqua undertone. plus, we had just moved in so there was no decor.

My kids are way older than your little ones and when recently repainting their rooms I let them chose any colour for one of the walls. One of them picked post-it-note blue (the other son didn't care) and the closest colour that I could find that he would accept was BM 2059-40 or Yosemite Blue. They love it but it is probably too strong to do an entire room wiht it. Blues are a tough colour to get right.

I don't personally have it, but a friend does. She used Sherwin Williams sleepy blue in a bedroom. It is so pretty. It isn't too light nor too dark. And it goes great with a white comforter. The next time I paint a room blue, that is the color I'm going to use.

The color I've used for my boys in 2 of their rooms is actually a color match. I used it when they were toddlers and shared a room and they've got it in our current house even though they're now 9 and 7. It's my favorite blue. It is the inside cover from the book My Truck is Stuck by Kevin Lewis. The boys loved that book, too!

Here's a picture. This was the boy's bedroom, but when we moved, we staged it as a girl's nursery. It's the only decent picture I have saved.

If you're looking for something a little bolder than the usual children's room blue, this is Ralph Lauren's True Blue. This is what an Atlanta designer chose for her son's room. I've linked to a picture of it below. The article said she wanted something that did not go purple or gray.

Here is a link that might be useful: {{!gwi}}

Kathec that's a darling nursery, and a wonderful blue. I love that room.

My younger son's room is BM brittany blue-- a pale blue with a hint of gray~ just yummy!

I really like that Ralph Lauren True Blue. I would prefer a stronger color in a medium - deep tone, but not too dark. Just friendly and fun, but somewhat classy that won't be a problem if we ever wanted to sell. I liked the photos I've seen of BM Buckland Blue but it just turned a little green on the wall. My very favorite color is like a lime green, so I'd like to accent it with that. I think I would actually prefer to paint it green and use navy accents, since we already know the curtains we're going to use, but DH is against that for some reason.

My son's room is an Ace color called Morning Glory. I painted it 6 years ago and I still love it, which is really saying something for me (I tend to second guess my paint selections endlessly after the fact). It's strong (so not babyish), not too dark or cold, and has enough gray in it not to be bright and in-your-face. It looked good with his navy/denim crib bedding and it looks good now with red curtains. I don't have a current pic (too messy in there!!!) but here is an old one:

Oh, and as a side note, we did this in Ace paint (their Royal Eggshell, I think) and the paint is holding up better than the way-more-expensive BM paint we used in my daughter's room. Go figure.

We painted the bonus room for our grandchildren BM Dolphin's Cove. I am not a blue person, but I love this color. We have lime green nightstands and they look great against the color. It is actually much, much prettier IRL.
Dee

When my oldest DS first moved into his room, we painted it a color similar to the pic that kathec posted. It was fine for several years but when it came time to repaint, we went with BM Quiet Moments and I looove this color. It can definitely make the transition from fun to sophisticated, IMO. I like the pick of Smoke above, too. I would lean more toward gray than blue. I find the "bluer" blues difficult to live with long term -- just my opinion.

Thanks for all the suggestions. I determined that the blues I like the best are pretty deep and saturated, and probably not ideal for little ones, so I've decided to paint Georgian Green with navy accents.

Groovia,

Your choice sounds adorable! Come back and share the results!

Groovia, I LOVE Georgian Green too. I used it in a powder room about 2 years ago and don't regret it. The navy sounds really great too.

Have you thought about doing a chair rail with chalkboard paint on the lower half? We did a chalkboard in my kids' playroom and the really enjoyed it. Hudson paint has a plethora of colors other than the standard black and green. I'll post their link below.

Here is a link that might be useful: Hudson Paint Colored Chalkboard Paint

Is the chalkboard stuff a pain to clean? I like the idea, but I'd hate to have chalk dust everywhere.

And can I just say, prepping the room is the biggest pain. You're all excited once you've selected a paint, and you have it there, just sitting there and ready, and then you have to tape. And patch drywall. And sand.
UGH!

We used Ellen Kennon, Dusk in our daughters room. I love love love it. It feels like the softest summer day always in there, even on snowy, gray days. It is so refreshing and happy. It is just right. The color is like a light sky on a pretty day. You can check out her colors on the gallery side. Her colors are full spectrum so they feel great!

Painted my Guest Room today, which is mainly occupied by my six year old grandson, a fabulous blue IMO, from the BM Affinity collection called AF-535 Serenata.I love it, nothing in my house is blue. It looks really nice with orange oak. These pics were taken at night. I'll add white wood blinds and search for new bedding, what an improvement, not sure if I should keep , paint or remove bench.

I think that all recommendations here are really nice. This would definitely help us out for the long run in order to make things work out. I really just hope that all would be well in this one for the future. Thanks for this one. Really appreciate a lot of things about this one!

Here is a link that might be useful: toddler bedding