With two sailors, four boards and plenty of different conditions you have a huge number of possible combinations to think about.
But lets start to think. The first two conditions to consider that in light wind (when you're on the Freestyle board) your wife might want something rather "crisp" and easy planing. And in high wind (when your wife is on the 62 liter) you might something rather control oriented and not to big. This suggests that the small board of the two ones you are buying should not be bigger than 70 liters and the big one not smaller than 80.
For the small board te options are then EVO 66, EVO 70 or Kode 68. Since your wife does not like classic boards, maybe the Kode 68 is not an option. Between the E66 and E70, the volume difference is not that great, but the 70 is quite a lot wider. On the other hand the 70 is also a tiny bit "softer" so the difference in application between the two is not as big as the 2.5cm width difference might suggest. Sail size wise, would say the 66 is only one notch below the 70, ie for you at 72, the 70 will cover 3.5-5.3 while the 66 might top out at 5.0 but be more comfy with a 3.5. The stronger and more powerful you are in your sailing, the further up the wind register you will be able to take the E70. I often use it all the way down to 3.5.
But the biggest difference between the two will be how much power they will need and be able to take when wave riding. With the 55cm width, the 70 start to work at very low riding speed (bad wave and/or bad technique). If will keep speed well and you can push it hard to generate speed also in slow wave. But when waves get bigger and cleaner it gets increasingly more important to really pin the board down in the bottom turn and set up the top turn in a big way. It handles also very good conditions, but you need to know what you're doing.
On the 66 on the other hand, you can more easily push to hard at slower speed and this will overpower the board. So it becomes harder to make it go well in slow waves and light wind (when it comes to the wave _riding_ - for planing, upwind work etc it is still very effective). But once conditions get better, the narrower 66 will be easier to keep on its rail also when you don't have such a "dedicated" technique. Generally, I think these differences will be felt more at your 72 kilos than or your wife at 54, especially since shoe will in any case be on the smaller board when its winds and/or big waves.
When it comes to the bigger board, some options are EVO 75, EVO 80, Kode 80 or even Kode 86. The Kode 86 will for sure be the one that carries 5.7 the best while still feeling lively and good for more B&J style sailing. It's a good wave board still, but with the wider tail it gets difficult in faster waves at your weight. The Kodes generally have faster rockers which means they need more drive (from the sailor - a more precise technique) to ride wave frontside if the waves are slow and the wind onshore. On the other hand they are both excellent for more fsw type sailing and particularly the Kode 80 is a fantastic easy and natural wave board in really good waves. I think that for you the step from EVO 70 (and even worse, from the 66) to the Kode 86 is to big. And for you and even more so for your wife, I think the Kode 80 will work well with a 5.7.
If you go for the EVO route, I think the 80 is the best bet. The 75 handles a 5.7, but the liveliness of the board suffers. The EVO 80 will in a way complement a smaller EVO in a better way. It will ride the waves you get in these light winds extremely well and it is still a good onshore umping board too. The question is how your wife will like it as a light winder. This is mostly a matter of taste. Some love EVOs for more freestyle sailing too (some of the Bonaire wonderkids that are now WC winners in freestyle used EVO 80s until quite recently). So if you like how these types of boards rides waves, there is a good chance this will be the best compromise for the two of you.
So my alternatives would be
A. EVO 66+EVO 80
B. EVO 70+EVO 80
C. EVO 66+Kode 80
D. EVO 70+Kode 80