I made my crew superhero costumes for last Summer Solstice. They were such a hit I gave them to all my nieces and nephews for Christmas as well. The capes were super easy - I got the idea from a cape tutorial I saw on Pinterest, but I didn't bother with the velcro necks. I cut initials out of polar fleece or felt for each child, and sewed them on.
To go with, I made matching masks and cuffs.

For the cuffs, chain 21. Ss into first ch (join 2nd colour) and chain up 2. DC around (x5 rows)At the end of row 5, ss and change yarn. Ch 1, and sc around. Ss to join, FO.

I used the masquerade mask pattern from Priscilla's Crochet for the masks.

I didn’t like the tie straps for young children so instead of ss and chains on the final row of the masks, I sc around until half way down the side, chained 45, attached at matching stitch on other side. Sc once on mask, turn and DC across chain, attaching with a sc under the start of the chain, continue sc around.

When you get to the other end of the strap, ss in the sc that attached the strap, pass your yarn skein through the mask/strap, ss in the second sc, and then sc to the end. Join with ss and FO.

Hopefully I've shared this in time to help some people out with late notice Halloween costumes, or early bird Xmas presents. (For reference, every child love them except the 10yo. My 8yo still plays with his, but less than the other kids - I'd say you should probably stick to 7 or under for this one, unless you have a huge superhero fan on your hands)