There are things that could have been done better. 1. Consider spreading the UN presence to other cities in Kenya, not just Nairobi. Eldoret, Nakuru, or even Kisumu could have used the infrastructure investment and maybe absorb the impact of extra people more easily than Nairobi.
2. Better PR. This has gotten around more like a rumor on the internet than the massive project it is. It deserved better news coverage and the UN + Kenya Government should have talked more about the benefits, tangible and otherwise, to the Kenyan people.
Though, given the low confidence many Kenyans, especially younger ones, have in their government, I suspect this is seen as just another power/moneygrab from the current regime and a concentrated PR campaign wouldn't have the impact it should.