If you want a busy seaside resort, I'd choose Shanklin. Sandown and Ryde are also good options, Ventnor is pretty but quieter. If you want to avoid big crowds, the West Wight is quieter, or parts of the East Wight (Bembridge, Seaview). Newport is convenient for getting around but is an average town, rather than feeling like a holiday resort.
There are about 20 holiday parks to choose from. The busy ones with indoor pools and near to beaches include Lower Hyde, Thorness Bay, Landguard, Nodes Point and Whitecliff. There are several that have fewer facilities but which are more rural and peaceful, and there a couple which are more expensive and are more like spa resorts (
see this holiday park guide)
Most accommodation providers will book the ferry for you, which is a lot cheaper than booking it yourself, but there are frequently discount codes and deals which make it more affordable.
My favourite beaches include Compton Bay (surfing), Bembridge (roockpooling), Shanklin (bucket and spade), Whitecliff Bay (sandy swimming) and St Helen's (kayaking).