The hubs will probably work just fine, but as Geoffrey says, you may want a few more spokes in the front wheel. This isn't a road race.
...and aero isn't going to be as big a player as lighter weight. You need to accelerate these wheels over and over and over in cross. If you can afford em, go with the same # of spokes, just carbon rims. Tubular is better, but its up to you. If the wheels are already built, you may be able to match the ERD with some chinese carbon rims for not too much money.