We produce our own Ukulele resources based on simple chords and begin by playing along with the original song. Any song that uses C, F, Am and G is playable fairly quickly. Once the pupils have got the hang of these chords we take away the CD and they sing and play. If you want to do a specific song the Chordie website has a good selection. The chords appear for guitar first but there is a ukulele convertor tool which gives you chord diagrams.

Use my Foxwood Songsheets. They were built out of adversity, and work for anyone. If your pupils know the names of the notes that they play, anyone can read them. They took a Special School to the Wharfedale festival, and the Sparrows to the Albert Hall. See my resources.

Ukulele:
Ukulele From The Beginning is a best selling tutor book and has a CD for backing tracks - ideal for classroom use. Your class will be able to play full songs very quickly just by learning a couple of chords. It is more suited to primary school age with the nature of the songs being 'O When The Saints' and 'London Bridge' etc... Book 2 and the Songbook is due to be released in the next month.
Other very good titles are 'Starting Ukulele' and 'Absolute Beginners' Ukulele.
Ocarina:
Ocarina Choo Choo and Play Your Ocarina (includes CD) are both helpful tutors. Due to be published in the next month is Ocarina From The Beginning which also comes with a backing CD. No previous musical knowledge is necessary for both pupil and teacher. Aimed at primary school age children.
Guitar:
The Complete Junior Guitarist is the perfect starter course for young guitarists. It includes advice, how to hold the guitar properly, tuning, basic chords and strumming. It enables your class to master the basics and more.

These can be found at any good music shop or online at www.musicroom.com Educators can sign up for 10% discount on everything.
Hope this helps!

Try and find out about Charanga Resources, who work with quite a number of music services, but schools can also buy into. They feature interactive activities you can lead from an interactive whiteboard, and pupils can access from home to practice with too.

http://www.booksforguitar.co.uk/ might be a start point