The idea is superb. I read the Landmark Thucydides, Herodotus, and Xenophon. For Thucydides, the maps are a wonderful addition. For Herodotus, they are less useful since the locations don't matter as much for the narrative arc. Or at least, having a map on the facing page is not as useful. Xenophon, I think the problem is that Xenophon's history is possibly the worst sequel of all time, and deserves to be as unread as it commonly is.
The translations are not the best available. Unfortunately. But Herodotus and Thucydides both repay rereading. If you haven't tried these, do! If you have, try a different translation the next go round.
I have Thucydides and Herodotus, both are amazing. I don't know how I would read Thucydides any other way. There are so many place names and directions, you really need the maps these editions provide.
The translations are not the best available. Unfortunately. But Herodotus and Thucydides both repay rereading. If you haven't tried these, do! If you have, try a different translation the next go round.