Move your eating window or do a longer or shorter fast to accommodate the dinner. If none is possible and your eating is messed up, do a longer fast later to make up.
This is the beauty of IF. You can be very flexible with your plan and yet be healthy and get results.
You could shift your window, narrow your window in anticipation of a larger meal, compensate (window- or otherwise intake-wise) throughout the remainder of the week – whatever it takes to reach a reasonable trade-off between shielding yourselves from (significant) overconsumption on the one hand and preserving what for you constitutes the minimum viable degree of social life. Over the long haul, striving for a balanced ratio of perceived cost over benefit typically outperforms eager over-optimization; sure, you may transiently gain a few grams of fat (or not lose as effectively, depending on where you’re currently at) during the weekend but what of it if you can promptly course-correct without it appearing a Herculean task.