I think maybe the message from all these reports is that you can probably count on nearly any major western resort that's still open the week you're considering having good conditions.
Spring skiing is one of my favorite topics and I posted a thread about it awhile back: http://forums.epicski.com/showthread.php?t=18431
The bottom line is that most resorts will still have lots of snow at that time. As a couple of earlier posts have noted, you can easily wait until March and see who's had the most snow and make your reservations then. You'll have almost no competition for reservations, AND you'll also have almost no competition on the hill once you get there
. Deals abound that time of year and the skiing is relaxed and comfortable.
Elevation can be a little bit of a consideration that time of year, so other things being equal (which they never are), the higher the elevation ot the ski area you choose the less chance you might have of running into really sloppy, slushy spring conditions.
I know Alta (if they're still open that week) and Snowbird are safe bets. We've skied A-Basin, Keystone, Breck, Vail, and Aspen in April and had wonderful skiing. Grand Targhee is outstanding that time of year but probably a bit limited in terms of a family ski week destination. I'm sure the California, Oregon, and Washington resorts would probably be good bets. And maybe this would be a great time to go north to Canada and perhaps even take advantage of a somewhat better currency exchange rate.