Thanks to your help, I've just ordered 3 great gifts for my sister's kids:
For her 4th birthday my niece will get a fuschia super-hero cape with a crown applique from superflykidz over at etsy (I was going to go for a play tent, but my sister had just gotten her one for the party. She's been pretending to be a superhero lately though, so I think she'll love this.)
New baby boy will get a custom-made sleep sack (the animal print one) from BeeBee Mod.
And proud big sister to be will get the cutest ever pink hoodie with a flower applique as her big sister gift, also from BeeBee Mod. And, I caught the final day of her big summer sale, so I got the hoodie for half off! Love that.
Thanks again for your help everyone. Smooches.