Not very good prospects for you James..... Fry in general, and then esp. Betta fry needs regular feeds at least 3 x per day during the developing phase.....you'll have to find someone very reliable and brief this person on every detail......(main thing of course... do not overfeed)
Liquifry no.1 (2drops 3 x per day) for at least the first 4 days (put a couple - I'd say about 4 - Apple snails in there as their excretion will also produce some infusoria and they will eat the excess foods- (Betta fry are of the smallest fry available)..... If you have a source of newly hatched brine shrimp, that'll be fine (2 feeds per day) for the following week, before you could go over to the crushed flake foods for egg layers.
A 25% water change (with seasoned water) every (approximately) 3 days will be great.... without syphoning any of the fry (of course)... Tough call...... I'd cancell the trip.
(Edit).... only realise now you said 2 weeks ago.... so those fry should be reasonably self-sufficient.... and already on the no2 livebearer fry flakes.... However.... still get the Apple snails.... do the water changes as suggested and feed 2 x per day.... Wet the tip of a toothpick.... put it into the (crushed) flakes.... & then just rinse it in the tank water.....
