You might be able to get them to keep your Grandfathered fee but at $10 not $7 or at least get it for two years if you get the Hopper, if they already are not you might also get the two year $15 package price reduction and freeze all for signing a two year deal. (Depends on their credit and if they usually pay on time) So $10 for DVR fee and $7 Joey fee would be $17. Three rooms $24.The reason they might is new customers often can get the $10 fee for the two year contract.
The advantage of the Wally's is redundancy and an ongoing lower cost per month. If the Hopper has a problem no TV though they only had one receiver till now anyway. And for two people one of the big advantages of the Hopper - all the tuners - isn't such a big deal. Three Wallys would give them 6 tuners.
However you have to buy three external hard drives for the Wally's (If they want DVR functionality and use of both tuners) And you have to pay a one time fee for DISH to turn on the DVR functionality. In addition you can't watch what was recorded on one Wally in another room - unless you move programs to the external hard drive and then swap the drives around.