I seem to remember one that my coaches did when i was younger (and i think it was to get height and also to help stop the dreaded pike lol) was the got about 4 pieces of pit foam and stacked them on top of each otherand you had to dive roll over them without knocking them down. Definitely helped cos it was much harder to pike. A way to make it fun can be to have a competition of who can dive roll over the most pieces of foam... i seem to remember many of these competitions!!
I have the kids dive rolls through the octagon preschool mat which is stacked on another mat for height. You could try a hulahoop even. Also I have seen coaches hold out a pool noodle and they have to dive over it (moving it further back each time for longer dives).
we start dive rolls with spring board and one or 2 8in mats and only move off of this station when we are happy with the shapes. Since they are using the springboard they can pretty easily get enough height to correct their shape.
it's not too hard to get rid of the pike from the spring board. emphasize changing direction so they are punching up and not just forward, squeeze behind, heel drive, flat and hollow shape in the air. sometimes it helps for them to think more about vault, like a dive to HS forward roll, than a dive roll in case they are piking b/c they are thinking about the rolling part.
from there we go to 8in mat no springboard, then 4in mat, then sting mat, then just spring floor.
We set up all the stations in a row so we can move them back and forth as need be and the extra mats take the fear out of the equation so they can "go for" the shape aggresively.
For the girls who don't realize they are piking, we have them put their hands along the front of their hips/thighs to feel what flat hips feel like. Then tell them to squeeze their behind and keep the front of their hips/thighs flat.
The best drill that i have found to help with teaching the not so horrible dive roll is to get a gymnast to stand next a box top (like the old school vault boxes..simply cause that is what we have, the object should not be moveable for the gymnast). The height of the box should be around hip height.
The gymnast start by standing next to he box (arms up to ear, or back whatever arm action you require). The gymnast pushes up onto his/her toes and keeping the belly button pulled in and bottom squeezed, the gymnast falls over and kicks/lifts the heels and flips over the box to a handstand. This needs spotting at first to get them to be confident, but after a while they are away laughing. The best thing about it is that very quickly (with correct coaching cues) the gymnast will learn when they pike, drop the head or arms, go loose, are not squeezing their butts etc..
I have had really good success with this drill.
On top of that i have them dive roll over a obstacle like the foam tower described above. And spotting it for shaping. However the drill is by far my best weapon haha, ontop of conditioning.
Its also important to remind the gymnast to learn to keep head up, look at thumbs, flip go up and flip..
I HATE the name DIVE ROLL as the last thing we all want is to have anyone diving. I call it stretch jump flip to handstand haha. i need a shorter name.
Hope that helps, please let me know how you find this drill if you (anyone) uses it
I know when son did them they seemed to look like they took off and then showed a real arch shape in mid air before landing - just found it on Youtube actually - called a hecht dive roll - is this what they need? or just not piking?