Yes - open plan schools and music are a challenging mix! First solution is to timetable music sessions as much as possible in a GP room or IT suite that has an interactive whiteboard, or can have a portable interactive whiteboard taken into it. At worst a laptop and some speakers will at least give you the audio, and using a projector means you can do everything but any interactivity needs to use the mouse or trackpad. If that is not possible, or doesn't give you the number of sessions per week you feel your class would benefit from, many ABC activities use the voice and movement and can be done in an open plan setting with reduced volume. This includes working and rehearsing in groups for P5-7 (Year 4-6). We would suggest you discuss the issue with your neighbouring colleagues and negotiate that you can make noise for the last 10 or 15 minutes of a session so they can expect it and plan their lesson around it. maybe they could come and be your audience and give you feedback rather than be distracted.
In this part of the lesson use percussion or your voices freely, or get the groups who have been rehearsing quietly to perform their compositions at full volume. Hopefully you will return the favour for your colleagues when they want to do music. This can create a useful dynamic - if the class works well and quietly during the quiet part of the class they get to use percussion and make a noise during the noisy part. Individuals who don't behave in the quiet part, don't get a piece of percussion during the noisy part!