Here is a list of equipment you might want to buy
5 metre USB Extension cable £2.28
Cable to connect mixer to laptop £1.30
Boundary Condenser Microphone £41
If you want to have a wireless microphone then this is a relatively inexpensive option although before you buy a wireless PA test your boundary microphone first as it may well pick up your questions from attendees at your event and therefore save the extra expense.
Portable PA with wireless microphones £124
Cable to connect PA to mixing desk £2.60