Should empty cardboard toilet paper tubes be used for pre-school craft projects?

For many years the local pre-school occasionally asks parents to save empty toilet paper rolls so they can be used for craft projects. The children enjoy making things like: robots, telescopes, musical instruments, etc.

Recently, someone pointed out that the tubes can be contaminated with E. coli from either toilet flush splash or someone touching them with contaminated hands.

Is this a valid concern? How long does E. coli live on dry cardboard? Are there any cases of children getting sick from playing with toilet paper tubes?