Blob Trees are an excellent inexpensive resource for assessing the mood of a group either at the start of the meeting, or at various points within it.
Essentially, they are an image of multiple cleverly drawn characters which represent different moods and feelings. The blob tree image can easily be posted into the whiteboard and then participants can be invited to place their cursor over the one that most closely represents how they are feeling – either at that particular point in time, or about a specific situation or event.
This provides you as a facilitator with an understanding of what is happening in the group, and it provides the group with a basis to explore those feelings and work out what to do about them.
The Blob Tree images are copyright, but they can be purchased image by image (for about £3 each last time I checked) for multiple re-use from https://www.blobtree.com
Track your progress to ensure the efficacy of this strategy.