I'd tell ya some sights to see, but they're mostly all pubs
What hotel are you staying in? Where is your group performing?
Seriously, be sure to see St Peter'*, Westminster, the Tower of London, and the gardens around Buckingham Palace.
For shopping and eating, stick to Picadilly/Regent Street/Bond Street/Covent Garden/Marlybone area (all within walking distance).
Stay north of the river. There is NOTHING to see on the other side, no matter what ANYONE tells you.
If you like clothes shopping (for yourself or your lady), window shop at Harrod'* in Knightsbridge (most elegant dept. store in the world), but BUY at Hennes & Mauritz (H&M) in the High Street area (low cost, high quality, up-to-date) .
P.*., you can get EVERYWHERE in London on the Underground.
And check out: