I would just get the visa for yourself incase you want to go to Ras mohamed /thislegorm . the rest of your family won't need one .

Naama bay is about 15/20 minutes in a taxi /courtesy bus . Entertainment is mostly hotel based but there is now the new Soho sqaure in sharks bay http://soho-sharm.com/soho-square-sharm .It's fairly new so I can't imagine it would have the same atmospere as NB (although a single trip to NB was enough for us) but it will at least give you somewhere to stroll, have a drink or a special meal . Believe there is bowling and an ice rink too.
Apart from that it's just dry desert .

Diving i am not sure about, but my family went to Ras Mohammed on a boat trip, never took passports and didn't have any visas.

Don't buy visa stamps if not going out of Sinai, eg to visit the pyramids/luxor etc. However if you do decide you do want to visit sites further afield when in resort later in the week, your tour operator will go to the airport for you and take passports and the the cash to get them stamped for you.

Hi

You can find all the Visa information you require in this existing topic http://www.holidaytruths.co.uk/viewtopic.php?f=32&t=189