Help ! how to care for abandonned axolots??

Hi, I'm new here. My son has suddenly left for Finland and has left me his 2 very large Axolots with NO indications as to how to deal with them. They are lovely creatures and very interesting to look at but they need to be fed and cared for for at least a month and I don't want them to die !! I think they have been fed chicken livers and when I realized what had happened (ie. son left suddenly) I managed to successfully fed each one 3 pieces of liver at room temperature. But where do I go from here?

How often do they need to eat ??
What do I do about water quality ?

I didn't count on having pets like that, that can't move with me (I'm rather active).

Thank you all for you help; they are lovely creatures and I want to do my best for them but I'm lost !
Djudy

They need a 25% water change per week, tap water is ok but you need to use a dechlorinator(if finland adds chlorine to the water or it has other heavy metals).Water quality is one the most important factors in looking after axolotls, poor water quality will kill them, if the water starts to smell or looks cloudy you need to do a water change as it has gone bad.
What does your son usually feed them?They are normally fed on pellets and worms, occasional treats bloodworm/shrimp/pinkies/guppies. Feeding times per week vary from person to person, but three or four times per week is ok.
The temperature should be10c to 20c, there is probably a thermometer attached to the front of the tank.
Contact your son to find out how he normally looks after these guys and give him a slap for leaving you in the lurch.
Check this site for other information, you will find all that is required to keep the axolotls happy and healthy.

Here is some wonderful easy to digest information:

Caudata Culture Species Entry - Ambystoma mexicanum - Axolotl

Caudata Culture Newcomer Articles

Caudata Culture - Frequently Asked Questions

Heres a rough list:
As xxianxx said 25% water changed each week, poo cleaned out every 2-3 days
Staple diet of night crawlers every two or three days, pellets or bloodworms as treats. Keep the temperature low.