Best choice is either the Beretta 391 or the Remington 1100. The 391 will win out on reliability, the 1100 will win on price. Don't bother with the cheap imports, they will be out of service more than they are shot. Both the 391 and 1100 have readily available parts and service, both can be field stripped and cleaned by a 10 year old. Both will limit the amount of felt recoil. Most importanly, both have been proven as skeet guns over the years.
For either one, cut a dowell rod to limit the magazine tube to hold only one shell, that way, when done on a skeet station there is less risk of a third shell having been loaded by accident.