It need to be all inclusive and so will have both day time and evening events, you have to find something that everyone will like. Its time to throw away the idea of the L Plates and move up-market.
Find a suitable Themed Party Venue that everyone will like; it has to have a central location that people can easily find and be near to popular and reasonably priced hotel chains.
The event needs to cater for everyone; the girls who go for nights out in the town regularly, the mums who no longer do this, friends who have financial commitments and don't want to over spend on an expensive hotel or a meal that is very expensive when the bill arrives. There are also girls who have busy lives and can't commit to two night and friends who might be slightly less adventurous and so can attend some events (but not all) of the events.
