What I am proposing here is not an event where we all get nekkid and roll around, the play that takes place would be PG, slightly kinky but nothing likely to land us in court, fun of the kind many of us are already doing outdoors and for that matter vanilla folk do, especially in the summer.
Food and waterfights in public are a big deal for us because we're used to it being done in a sexual context, the reaction of many on seeing fully clothed WAM is, "That's a fetish?!". Someone left a comment on one of our Youtube videos describing it as "silliness in dresses", I couldn't have put it better myself.
The idea of the MBP is not for everyone and it needn't be, the idea of this discussion is to feel out who might be up for it and who isn't (I want concerns to be raised too, which they are being, so thanks for that

Hayley - good point about the weather, have to think about that one (maybe a case of choosing locations with alternative plans available in case of storm and tempest).
Messy meal indoors - the problem with this is approaching a venue and basically asking if we can book the place with the specific intention of getting raucous and causing a huge mess. Even if we promise to clean up thoroughly and leave the place as we find it it requires a very understanding and trusting owner and probably some kind of large deposit in addition to whatever it costs to book the place in the first place (there is no way any restauranteur would ever allow anything of this kind to go on with other diners present, it would be suicidal to their reputation).
For things that require booking, I'm still keen to book a day out at the World's Muddiest Assault Course near Cardiff if people are up for it (see threads passim).
Andy - the beach sounds great! It doesn't have to be a totally pastoral location, so long as it isn't actual unpleasant (we can do better than a picnic next to the ICI plant at Fleetwood, for example).