So, be prepared. Find out if there's any chance of getting new computers. OK, no new machines. OK, time to be creative.
Old machines are useable, and can be put to real work in the classroom.
The most commonly used application in primary classrooms is word processing. There's nothing wrong with this. I'm not going to buy into that argument here, except to say that with practice and coaching a word processor is a powerful tool in the hands of any user, no matter whether they are 6 or 60 years old. Any old computer you will find in a classroom will do word processing. So it won't run Word 7.