Graham, to try and meet your requirements I suggest the following.
Nodes Point Bembridge.
It is a very commercial Park Resorts site so has bar and entertainment on site.
There is the ONLY fully dog friendly beach with direct access from the site at the botom of the hill.
Shops and eating places are available in Bembridge for convenience, or there is a 24 hour Tesco about 3 miles away towards Ryde.
Ryde is a very good place for shopping and eating places.Buses are available in Bembridge, but it is a bit of a hike.
Whitefield Forest, near Ryde.
Just on the outskirts of Ryde, a very good site but very limited dog walking on site, but only a very short drive from Tesco.
No bar or shop on site, so Ryde is nearest for those, and the main bus terminal to access other parts of the Island.
Southland at Sandown is quite far away from everything.
The Orchards is an OK site, with shop but nearest pub is about 4 miles away.