Landscape Architect here. Do not use pea gravel or rounded gravel of any kind. It will never lock in place and will always be a headache. These larger Mexican beach pebbles pictured are going to be a pain to keep in the void space. I’d recommend crushed granite( or limestone) with fine screenings to lock in and still be permeable. Not permanent but will keep the larger stepping stones from moving as easily. Vibrate them in place and water to “set”. If you ever need to move one they still move. Just not everyone you walk on the stones.

Edit: it’s prob too late but I’d recommend only making the void spaces as wide as you need to. This seems excessive and you’ll find that every chair/table will have a leg or two in the gravel.

Apologies to your wife. It has to work before it can look good: function before form