Q. Can a mixed fruit salad, made by cutting fruits including grapes be prepared on Shabbos?

A. Some Poskim maintain (see 39 melochos p. 334) that one should preferably abstain from cutting grapes on Shabbos, even if one does not intend to squeeze them at all and will not drink the juice that emanates from them.
Horav Shlomo Miller’s Shlit”a opinion is that one can be lenient and cut grapes for a salad or for a child, if the emanating juices are discarded.

Rabbi A. Bartfeld as revised by Horav Shlomo Miller Shlit”a