At the city park, 3/4 of the park is used for the playground, 1/3 of the park is used for picnic tables, and the remaining space is used for restroom facilities.

Does it make sense to say that 4/7 of the park is used for the playground and picnic tables combined?

No, it does not make sense to say that 4/7 of the park is used for the playground and picnic tables combined because the total space used for the playground and picnic tables is 3/4 + 1/3 = 11/12, which is greater than 1 (the whole park).