Need help with watering cattleya seedlings

[greyblackfish]

I've got three cattleya seedlings a month ago. I'm going out of town for at least 4 days and I'm worried about them.

I'm really afraid to really wet the moss medium as much as I do with my other seedlings. They are potted very loosely in sphagnum and a bit of bark so the pot doesn't retain that much water. I've killed a cattleya seedling not long ago from rot and it's made me very paranoid about watering. I do a weekly watering which always worries me. Then it takes 2-3 days for the medium to dry out. By the fourth day the moss is crispy so I give them just a little bit of water every other day until it's time to water again.

I'll be gone for a while. It's been hot here. Got any suggestions for time away? And any suggestions for a better watering system than the one I have? Thanks in advance!