LED Strip Controller - Can someone check over my schematic?
Good news. You've picked mosfets that can work with a 5V gate voltage. Not the best case, you might experience fairly high Rds(on) and they might become warm.



I'm not sure of the purpose of the booster. Why do you need 24V LED strips when there are also lots of strips for 12V?  

However, this 2A boost converter could work. The board layout is very important at 1.2 MHz though.
I would recommend for a first design with switchmode supplies to stay in the  KHz switching range.

I also have a few other remarks:
 - Add an LC input filter to prevent noise upstream.
 - Add more than 22uF output capacitance.
 - Make sure the gates and the on/off are at a known level during reset with some pull-up/down resistors.
 - Add at least some 100nf and 1uf ceramics around the chip, and preferably some 10uF electrolytic near the connector.

I can't comment on the ISP connector, this will be entirely up to the symbol/footprint connections.