If you use the watery super glue it will not give time to set it. Water acts as an accelerator. Use a gel type give you more time before it sets up. I know the mushrooms produce a little slime making it hard , sometime's it's better for them to be wedged and attach themselves. Ever use frags and glue directly to them could work better since you have a sand base. Back in my haydays ( I'm old) I used them with success.
Here's a few videos that may help :
https://www.bing.com/videos/search?q=ho ... ORM=VDVVXX