Hi,
I'll be staying in the Santa Fe in June which will be my second time in that hotel so I think I can offer you some advice.
The Santa Fe often gets a bad rap just because it is the budget hotel but this is simply not true. It's a beautiful hotel and by any other standards it would be 3 or 4 star. Reception won't be exceptionally busy but your never usually kept in queue for very long during check-in. In the reception there is a very small kids corner but it isn't really necessary in Disneyland! There are a few TV's scattered along the walls showing Disney programming.
Your probably aware that your room will be located in its own 'peublo' or block and all other amenities such as the bar, restaurant, shop and arcade are located in the main building. There are a number of flat blocks and a number that are taller. You'd be lucky to get a room at the top because the views are quite nice. There is a stream that flows down the blocks through the hotel which makes an added attraction along with the various Mexican themeing. There is a maze and childrens play park to the left of the main building (you have to go up steps).
The rooms, while basic, are beautiful. Each room has two double beds, a phone (leave a credit card at reception to get access), a remote tied to the bedside table, a chest of drawers with a TV on top that receives Disney Channel in 4 main European languages (incl. English), A french general entertainment channel, BBC World, CNN and something German. On Channel 1 there is a guide to help you get the most out of your stay. The bathroom is very nice and should be very clean, they replace towels twice a day normally. They leave plastic tumblers in the bathroom for drinking/cleaning use. The shower/bath has constant hot water so don't worry about getting froze.
They offer you three times for breakfast (7,8,9am). Don't take 7, you'll never get up in time. Always be early as the Santa Fe can be notorious during breakfast as it sometimes resembles an army base at chow time. Try and know basic french for certain food items so you can request to the chef behind the counter if he has a certain item. It's not necessary but it helps.
Anyway, hope you have a good time and enjoy this great hotel.