Mithriltari- I have all my CP stuff through for Whinfell so I can answer any questions you have.
Try the code JAN8CP when you enter your search for accommodation, it should give you about 15-20% discount providing you are going in term time, not sure when this promotion ends though.
Basically all that is included in your price is your villa and the swimming pool. Everything else you pay for.
The spa - depends on whether you want a treatment or the World Of Spa 3 hour thing where you can visit all different steam rooms, foot spas, waterbeds etc, this costs £27 mon-fri 1pm-9pm, £32 mon-fri in the morn, or £35 sat and sun. There are ladies only sessions Tues and Sat. But if you put your wee one in the time out creche you can have a 2hour spa session for £24. Creche has a "taster" session for 30 mins so that you can meet the staff etc. If you use the creche then 3hrs is £18 and 2hrs is £12.
Bikes - mon-fri adult mountain bike £21 and for treking your wee one around I would recommend a trailer so that would be £36 for the bike and trailer.
We usually eat out for a lunch and have dinner in the villa but my two are 5 and 2. Messy play is fab, ds1 did it with my DH while me and my friend relaxed in the spa!!!
It is kind of a club Center Parcs in that you only seem to be given the information when you have booked it.
Even when it rains at CP people are still out and about in it, we even managed to experience snow and were swimming at night outside whilst being snowed on, magical.
Just post any further questions on here and I'll answer them.