Every time I use a tool on my boat, I buy a duplicate that stays on the boat. Don't forget a big flathead screwdriver with vice grips so you can manually trim down the motors when trim hydros fail...
Buy new fire extinguishers. I tried to use one off my boat to put out a brake fire. The gage read green, but nothing came out. They say all the pounding compacts the powder; I'm a believer now, will be stowing mine flat from now on and rotating.
Check the dates on your smokes and flares.
Take 2 5 gallon buckets. Before leaving the dock, test your front and rear bilge pump auto operation by dumping 10 gallons of (preferably fresh) water in the access hatches. I do this yearly so I can see how and when they come on. I do it in the water, not on the trailer because the boat is bow up on the trailer.
Check every switch while running, lights, pumps, everything. You may discover loose connections/grounds, etc.
Take video, then watch it later. You might notice things/sounds you missed 1st time.
I think the others have, or will cover most everything else.
Rule #1, Enjoy, it seems you have worked hard to get to this point!