Exactly - all the parks have lockers, and moreover there are two locker sizes - so if you find your tripod doesn't fit in the 'small', you can check the large too - maybe it'll fit in those. It's tripod-dependent - most travel sized pods should be no problem - many 'standard' sized tripods may still fit - many large, heavy-duty, pro-level pods may not. And it depends on what head you have on it. Remember the properties of a rectangle - the cross-diagonal is the longest measure - so try running your tripod from the upper right back corner to the lower left front corner as a last-chance resort to see if it'll fit.
Remember too, when you rent a locker at one park, and go to another park the same day, you keep the receipt when you check out the locker and return the key, and when you get to the next park, you don't have to pay again for a locker. The locker fee is per diem, and transferrable across parks.