So...I gotta ask. Is Cornwall a desired destination?
Have you done the 'Woo Central' sites of Stonehenge, Avebury, Glastonbury, and Bath, along with the option to nip in to the Cotwolds? I ask because they are all grouped north of your two functions, while Cornwall proper is considerably west ('considerably' being a relative term UK/US-wise).
Bournemouth is roughly the same distance east of Exeter as Penzance is west of Exeter.
I think if I were intent on Cornwall from Exeter, and I was driving, I'd head west from Exeter to Tintagel, then southwest down the north coast to Newquay and St. Ives, then bump over to Penzance, and then back east along the south coast, through St. Michael's Mount, Falmouth, St. Austell, Plymouth, Torquay, Exemouth, Weymouth, and finally, to Bournemouth.
The 'Woo Central' route is north to Glastonbury, then clockwise through Bath, the Cotswolds, Avebury, and Salisbury, before arriving back in Bournemouth.
Not that Cornwall is short on good stones.
You don't strike me as the aviation museum type, but if you are, there is supposed to be a decent
Fleet Air Arm museum in Yeovilton, about half way between Exeter and Bournemouth.