First check that your ticket is indeed for the 2:29 departure. By default train tickets are for a route, not a train, so you do not need to do anything at all if you want to take another train than you originally intended.
So if your ticket is a normal ticket, that SBB clumsily calls a “point to point” ticket, it will be valid for one trip from Interlaken to Geneva, for any departure on Jun e 30th, till 5:00 the next day.
Note that with the 14:29 departure you are at the airport at 17:37, which may still be early enough. Certainly if flying to somewhere in Europe. Myself I would probably half an hour earlier though.