Ask HN: Pre-school educational software

Hi all,

I've recently come into a bunch of older computers (P4 and up, 1GB RAM, 20-60GB HDD typical) which I'm planning to fix up and donate to my son's daycare's kindergarten and pre-kindergarten classes (ages 4-6).

I'm trying to convince them to not buy MS licenses, and I'll install Ubuntu for them (standalone machines only).

Does HN have any suggestions for educational software packs for linux (ideally free) that's age appropriate and proven? Also, has anybody done this, and have advice to give on setting them up to require mininmal tech support (which I would likely have to give)?

Thanks!