BW has an Easter Egg hunt (both Mr and Mrs Bunny usually show) and craft events but 12 year olds might not care for either.
Easter time (week leading up to Easter and week of Easter) is extremely crowded -- most crowded of the year along with Christmas week. Makes the huge summer crowds feel light. However, weather is ideal -- 80's to low 90's, not overwhelming humidity, and usually not much rain. Also understand that Disney does not get elaborate for Easter like it does at Christmas -- you will see some additional decorations but nothing of moment and an Easter bunny (the White Rabbit with a basket) sometimes is seen in the parks. Also, you should not go with the expectation of seeing and doing everything -- because of crowds you just may have to skip some of those popular rides. Based on 13 Easter trips, I provide the following suggestions:
1. Don't go to MK on Easter Sunday. It is a sardine can that day. Many go there that day for the believed "special" Easter events that only occur on that day. Guess what? There aren't any. There is an Easter parade which is merely the daily parade at 3 with Easter theme floats added. But it shows everyday of the week leading up to Easter and on Easter. Thus, go some other day. MK restaurants don't change a thing on Easter. In other words, avoid MK like the plague on Easter Sunday unless you really like huge, huge crowds. Epcot usually has its lightest day of the holiday season on Easter Sunday. Even MGM and AK are lighter than normal. (Note anytime I speak of lighter crowds herein remember it is relative; I am simply saying it is lighter than the usually stifling crowds for that time of year.)
2. MK is extrmemly packed everyday and the day before Easter and day after Easter are among the worst days. Good Friday, always seems a little lighter than other days. But lines will be huge and fastpasses for popular rides can run out for the day long before noon. Epcot crowds fluctuate the most and lighter days can be found during the week although it is never certain which days. During a number of Easters, because the expected crowds were so huge, Disney has changed Early Entry by simply opening all the parks early everyday to everyone. No announcement is made until just before the two Easter weeks begin and sometimes the decision was made mid week towards Easter and announced the night before for rest of Easter period. Moreover, we only found out about it the first time we learned of the practice by reading a page ten story in the Orlando Sentinel while at our hotel at WDW -- the hotel had not even mentioned it; thus check with hotel when there to see whether they are opening parks earlier than scheduled.
3. Most crowded times of day at any park are 10:30 to 3 (and during which is a good time to spend that needed off time back at the resort). If you go early you can hit some things without long lines. But by 11 in the morning you will usually see 80 minute and longer lines (much longer very often) for popular things and it stays that way all day and evening (with some exceptions , see below) -- those are: (a) at MK all three mountains, Pooh, Dumbo, Peter Pan, Buzz, Alien, Jungle Cruise, Astro Orbiter; (b) at Epcot Test Track (which goes to lines of 3 to 4 hours); (c) at MGM Rockin Rollercoaster and Tower of Terror, Millionaire (though waning), and Mermaid; (d) at AK, Safari, Dinosaur, the new mad mouse like coaster (off hand cannot recall its name -- and yes I do believe it is a forgetable ride), Kali River Rapids. Use fastpass for any of those if you can.
4. Other rides and attractions can have very huge lines in the morning to early afternoon and then often by 4 at MK and AK and 3 at Epcot and MGM the lines are fairly short and sometimes non-existent although they can have crowded spurts (like when a nearby theater attraction lets out -- never ever leave a theater attraction, such as Indiana Jones, and head for the next nearest attraction (in that case Star Tours); Half of the people leaving that theater show do just that causing a huge line at he next nearest attraction for a while). MK gets a bit lighter between 4 and 8 and then explodes to huge again as the masses return for nightly parade. AK is lighter after 4:30
5. If at MK, AK, or MGM you can't get a fastpass for that must have popular ride, try hitting it during a parade or during the first Fantasmic (when there are two a night -- often during Easter) at MGM as lines can shrink to 30 minutes at those times. Also, MK stays open very late -- used to be midnight every night, a hurt-the-customer-budget-cut-shrink to 10 and 11 some nights this past Easter -- and you can sometimes hit those popular rides during the last half hour with smaller lines.
6. If you want to eat dinner in a sit down restaurat in a park, make a PS. I was once at Crystal Palace on the Thursday before Easter at 6 when a family of four walked up and asked what the next available time was in the evening that they could get seated and the CM said Tuesday. Somewhat of an exaggeration but not much. Some of the resort (not park) restaurants have Easter brunches (I know Chef Mickey's and Park Faire do, and possibly Cape May) but you need to make ressies long in advance and I beleive they now require credit card number to hold. Note, you can, at many places, particularly resort restaurants get a ressie by just calling the day before but it is very important that you make a ressie and don't just try to walk up.
7. Highly recommend avoiding waterparks during that time. I know that is blasphemy to some but it is simply meant as fair warning -- those things fill to capacity by 11 and don't let up at all till 3; people who arrive early commandeer all seats and there is nowhere to sit all day unless you are one of them.
8. Easter was the first time we experienced the two hour or longer parade squatters -- people actually start commandeering prime front space for the afternoon MK parade 2 hours before it begins; some of those actually sit in the sun the whole time. Recommend you just wait until shortly before the parade begins, find an elevated area like outside Town Hall on the stairs, and watch it from there.
9. If they have two Fantasmics a night, go to the second one -- the first fills to capacity and you need to head there more than an hour early to assure getting in. The second never fills to capacity and thus you can walk in at the last minute. The same apples to Spectromagic at MK -- when there are two a night, the crowd for the second one is always much lighter than the first.