Beer ice cream?
Ice cream needs very small ice crystals to make it smooth. You would need to eliminate the alcohol from the beer to began to make it work as an ice cream ingredient because alcohol interferes with the formation of the small ice crystals. You might achieve a sorbet using the beer, but I think it might still be best to heat it first in order to eliminate all or most of the alcohol before including it in the mix. If you have an ice cream maker (one of the modern varieties) why not give it a try once or twice betore your scheduled party to see how it works out for you.