Are you watching the dogs when they are outsoide? They may well be digging up the lawn as well.
If you want to have a lawn and dogs.... for dogs that are tearing up lawns or killing them with urine, you'll need to take the same steps you would if they were acting this way in the house:
start to train them to wee in an area you designate and take them there on a lead, and train them to a word so they know to sue this area only
keep an eye on them when they are outside so that you can redirect behaviour if they are digging to doing something else
consider creating a digging area like a sandbox just for the dogs so they can satisfy this instinct -- then redirect them there
If you have two puppies at the same time all of this is considerably more difficult -- that's one of the major challenges of taking on two at once -- they spur on unwanted behaviour and are harder to manage (because iot is hard to try and tell two at the same time to refocus).
You may need to seaparate them so that only one goes out at a time to help in training and general management.
Be sure to read thru the thread in the Library on tips for raising two puppies at once. They need a hige amount of solo time and individual training time to help avoid challenging behaviour and to keep them from bonding so closely to each other (especially with siblings) that you are always low on their totem pole and in their mind, not really necessary to obey. To get your lawn back you are almost certainly going to need to work on solo training and keeping them separate for outdoor play, except for supervised periods when you are there and managing both.
You'll need to keep them both off the lawn anyway for several weeks while you reseed; or else to lay new sod and allow it to root properly.
Also taking them out so they get lots of walks and play in other places than the garden should also tire them so they are less inclined to tear up the lawn. getting them into obedience and then practicing with them is even better as using their brains this way will tire them FAR faster than playing -- I guarantee it!!