Prakriti
Hi, I'm a Mindflayer, but don't let that worry you
For combat, I'm going off of the idea of assuming over time the rolls you get will average out. So, if the wolves need to roll 16+ to hit their target, then 25% of them will hit each round. So then roll the d8 to see which ones hit, and apply the average damage as per the MM.
That's pretty much how the "Handling Mobs" rule works in the DMG (p. 250). You just assume that a certain number of the creatures hit depending on their attack bonus and the target's AC. For example, for every 3 orcs surrounding a fighter with AC 19, 1 will hit; the others will miss (there's a handy chart for quick referencing).As far as running them at the table... I'd control them as DM. Probably wouldn't even roll to hit for each summon. I'd have some work to provide advantage for the others (cutting down to hit rolls), use average damage(cutting down damage rolls) and maybe just assume like 3/4 or half the summons hit with their attacks(not roll at all).
This could work really well for Conjure Animals if the summoned animals are handled by the DM. But it could bite the player in the %*# if you don't tell them how the rules work. If the player spreads their elk too thin, such as 1 or 2 per enemy, then, "Sorry, they all miss." So if you want to involve the player, then you should do the calculation yourself, and tell the player how the math works out: "For every 3 elk on a target, 1 will hit." Then use the average damage instead of rolling.