Cleaning fry tank gourami

[hils]

So my gourami fry are about 2 weeks old, tank is wrapped in plastic, has a doing filter going and a heater. There's no substrate on the bottom, but I'm wondering if I should clean it, or how to go about water changes without upsetting them or the air temp. I'm worried I will vacuume up the babies.
At present the ammonia and nitrites are 0, the nitrates are 15
I'm heading away for three weeks on Saturday and my neighbour will feed them.