Even a set class can have a wide range of abilities.
Ensure that your questions are suitable to the range of abilities in your class and make sure that you have a little extension work up your sleeve.
You may not need it, but your observer will undoubtedly want to know that you are catering for G&T. Ensure that you have made provision for other SEN and have considered how your TA/LSA will be deployed.
If possible, try to include a multi-sensory aspect within your lesson. If that doesn’t meet well with the lesson objectives, make sure that you have a range of elements to your lesson that will meet a number of different learning styles (auditory, kinaesthetic etc).