Hi clem,
The Cheyenne is a well themed Disney budget hotel, more interesting and attractive for kids than the Santa Fe IMO, and just slightly more expensive. I stayed here for the first time in January for a few days, and was quite happy and comfortable, even though I am used to staying in the more expensive Disney hotels. You can read my review with some photos on TA. I have included as much info and detail as I could at the time.
www.tripadvisor.co.uk/ShowUserReviews-g226865-d262686-r96370316-Disney_s_Hotel_Cheyenne-Marne_la_Vallee_Seine_et_Marne_Ile_de_France.html
Regarding Half Board, you can choose Standard, Plus or Premium category which gives you one voucher per person per night of your stay ( so you would get 3 per person aged 3yrs and above. ) Everyone in the booking has to have this - you cannot just book it for some. The saving is not huge, but can certainly add up for a family over a few days, as the vouchers also include one soft drink or bottle of mineral water ( still or gassy ) per person.
You can use these vouchers to cover lunch or dinner in the specified restaurants, or use them like cash in more expensive ones and pay the extra. They will deduct the vouchers from the final bill. You do not get your usual included drink though, as outside the HB plan.
You cannot add two together to pay for a more expensive meal -e.g. four people dining can only use four vouchers.
The French are not very good at fast food, although the fish and chips in Toad Hall in Fantasyland is good ( one meal with 2 pieces of fish in batter with chips was enough for 2 of us to share for a quick lunch ). Pasta and pizza in Pizzeria Bella Notte and Colonel Hathis are fine, and we also like the Mexican fast food in Fuente Del Oro. Last Chance Saloon with ribs, burgers etc is also popular.
We usually have a good breakfast ( you will see many people putting croissants, ham, cheese, fruit etc into bags from the breakfast buffet and also filling up bottles, beakers or flasks with cold drinks or tea/ coffee to take into the parks ), then we only need a small snack at lunchtime from a food stand to keep us going, before having dinner later. Sometimes we have a late lunch around 3pm in one of the buffets which are all you can eat, so good value for money. ( plenty of choice, with starters, soups, mains, desserts, cheeses, including vegetables, salads, pasta, meat, fish, etc with a section of foods that kids often like as well.
HB Standard vouchers covers the buffets in the parks, ( except Buzzs Pizza Planet buffet ) Hotel Cheyenne, Santa Fe, and also the Tex Mex buffet in La Grange restaurant in Billy Bob's in the Village. You can use them for a 3 course meal with choices in Silver Spur Steakhouse in Frontierland, and also for Cowboy Cookout BBQ also in Frontierland which currently has Character Dining with Woody, Jesse and others.
They also cover Annettes Diner in the Village which is themed like an American 1950's diner, with some of the waiters on roller skates. In the evenings they do a short show every hour. The burgers here are far more like the ones you find in America, with good sized portions. I had lunch one day here in January, and could not eat it all. Lovely ice cream milkshakes as well. You cannot make reservations here, just turn up and wait. Open all day until late at night. ( see reviews on Trip Advisor ).
HB Standard also cover Crocketts Tavern buffet, but you need a car to get there, as inside Davy crockett Ranch.
There are no hidden charges in the Disney hotels or resort. Everything in both parks is included in park tickets apart from a small amusement arcade and a shooting gallery, which are not worth bothering with. Spending money depends on how much you eat, and how many souvenirs you buy!
There is an ongoing Prices thread on the DLP/ MLV forums which posters add to.
There are two forums for DLP on Trip Advisor where regular posters answer questions and help with trip planning. The are both linked.
www.tripadvisor.co.uk/ShowForum-g2079053-i21935-Disneyland_Paris_Marne_la_Vallee_Seine_et_Marne_Ile_de_France.html
www.tripadvisor.co.uk/ShowForum-g226865-i2224-Marne_la_Vallee_Seine_et_Marne_Ile_de_France.html
There are quite a few topic threads on Mumsnet about DLP, so scroll through to find those for more info as well.