3 week vacation - prep plan?

[604reefer]

I'm leaving my tank for the first time (gahhhh! ) and I'm nervous because I'm gone for 23 days. Could you critique my plan?

Background:

- 20 gal, no sump, no refugium
- in-tank protein skimmer and surface skimmer
- LPS and mushrooms only (monti cap should be ok)
- tank has been running very smoothly for 9 months (touch wood)
- friend with no reefing experience is going to check on the tank

Plan:

1. ATO setup with 5g reservoir and more in another bucket in case running low
2. Auto feeder setup, all friend has to do is reload the compartments after day 14 with my set amount from a separate daily pill box
3. Friend to empty/clean skimmer cup/surface skim filter as needed
4. Friend to scrape inside glass w/mag float, avoiding sand
5. Monitor for anything dead and remove (conch/fish primarily)

Concern
No water change over 3 weeks on a 20 gallon. I usually go 7-10 days before a WC. Going to do one tomorrow and one next Wed. Should I feed a little less over the 3 weeks to compensate?

Am I missing anything?

Thanks yall!