Plenty of reviews of Ventura from the link at the top of the forum - including a couple from me!
It's a family ship so there will probably be a lot of children on board - potentially 700+
Any mobile connections cost a fortune when out of range of land based stations - you are better to wait until you go ashore to use wi-fi or use the on board computers, but they aren't cheap.
Dress code - smart casual for 5 nights out of 7, formal the other 2 (10/4 on a 14 night holiday)
Excursion info is available on P&O website at least 6 weeks before you travel. Expect to pay £30-250 depending what is on offer - typical is around £50 for half day and £90 for a full day.
C deck deluxe cabins have the largest balconies of this grade so plenty of room.