If he bought a new bike that uses a 7 speed freewheel drive system then it says to me that it's a less costly bottom range bike. Likely he's looking for CHEAP reliability. So this advice is likely going to be the least costly and have the most likely chance of success at a lower cost.

The problem is that having ridden the new bike long enough to break some spokes already it means that the others are now well on their way to breaking as well. So it does little good now to replace the broken ones even if you went on to add tension to the spokes to better support the wheel. The damage is done.

What may happen with the new spokes is that the nipples may start to deform or even pull through the cheap rim. If that occurs then it may call for putting a new double wall rim and spokes onto the hubs.

If it were a wheelset with a higher end gearing setup I'd suggest just buying new heavier duty wheels and tension them correctly. But in this case I doubt you can locate a 7 speed freewheel hub wheel set that has a higher end rim. At least not without going to something like the Phil Wood hub wheels which could cost well more than the cost of the bike. So you and he are stuck with rebuilding the existing hubs into a wheel which will work for him.