Nice whad. Been three times now to Malta and can't wait to go back! We stayed this time in Attard with family - so very easy access through Ta Qali to the western less populated side.
MTB was hired through http://www.thecyclistmalta.com/rentals.html at 10 euro per day for a very basic Corratec X-VERT hardtail. I just took my pedals, helmet, mini pump, saddle bag with tyre levers plus repair kit, and shoes. They supplied the spare tube and could have supplied a pump and helmet if I needed it.
Happy to PM further on rides (either road or MTB) and can put you in touch with road and MTB groups if you want to ride with others. The later in particular would be helpful as there are no specific MTB trails, rather small lanes and tracks; so would be good to be guided to the better rides unless you know the island well. Unfortunately I couldn't ride when the others were so just followed my nose. This did mean quite a few dead ends but enjoyed exploring!
This will be my first trip to Malta. Old man is Maltese but all relo's have relocated to other parts of the world. I will PM you closer to my departure time for further info. BTW, great pics.