So for my campaign I'm working on, the group will be being chased by a boulder.
They will be around lvl 3 and it shall be one at a time, as the idea is in reference to a crash bandicoot level(lol).
I've read the chase rules and plan to have an item they can use to buff for the checks.
I would prefer it be one type of check with varying DCs. Needing help in balancing the buff item to make it possible for all to complete without massive retries, and to get the DCs doable for the checks.
Seems to me like a quick chase in which the pursuer is inanimate (thus doesn't need to make skill checks) so it changes the dynamic a little.
The characters need to keep pace ahead of the boulder, because it will relentlessly stay at their heels, keeping its pace regardless of obstacles.
If you only want one check (I'm not quite sure why) then Athletics seems to be the best for *running away from a boulder*. It may involve jumping over or crawling under obstacles in the way (which Acrobatics would also be appropriate for).
It seems to me like you want to make sure the players definitely get away (one skill, giving them an item that buffs that one particular skill), so I wouldn't even decide on DC. Just have them roll for each obstacle, if they roll over 10, they're good and keep going, but if they have made some headway and you want the boulder to catch up to keep the tension, increase the DC on the fly.
I would advise to allow as many different options as possible. While a wizard might be terrible at running, they have access to Expeditious Retreat and suddenly can outpace any athlete for the duration, etc.