Immersive augmented reality with head-mounted displays is increasingly being researched for museums and cultural heritage sites. However, the isolating nature of the devices is at odds with the usual group sizes of visitors. This paper firstly provides a systematic literature review of the field of co-presence as a quality of experience in immersive AR. Based on these findings, a collaborative prototype is built using a research-through-design approach. We then report on a preliminary evaluation study (n = 20) to assess the effect of the prototype on communication between participants. We conclude that there are still few solutions for delivering collaborative and playful immersive AR experiences in museums, but early indications suggest that it is promising.