WHAT IS THE BEST HOLE SAW FOR CUTTING A 3" HOLE 25 TIMES IN 1" RED OAK THAT LEAVES A SMOOTH HOLE. I PLAN ON USING THE PLUG FOR A PART OF THIS PROJECT

You'll want to use a hole saw that is designed for wood specifically and not a bi-metal one for example.
As far as the smoothness, one with more smaller teeth will achieve a better edge result, however it will cut slower though one inch of oak so you will have to go slower on the cutting pressure so you do not create burning. If you are using a drill press, you might want to lift the bit every once in a while through a cut and blow out the sawdust.

Is there a "rule of thumb" as to how wide the boards should or should not be when gluing together to make a panel.
Say I want to make a 10 inch panel. Is it best to use two 5 inch boards, or use 5, 2 inch boards.
The two panels that I'm planning on doing will be for high chair seat and tray.
thanks.

I apoligize for the delay in answering.
People tend to keep boards about 5 inches or less when glueing up a panel.
Also, you want to keep the panel balanced so that it doesn't curve. Take a look at the end of your boards and you will see the ring pattern. You'll want to alternate the curvature that you see on the ends. This means that three boards is usually the minimum because with only two boards, you can't really avoid a tendency to curve as well.

I have an old boat building plan that uses the following wood types. (Oak, Fir, Mahogany and maybe African Mahogany?)

Can you please recommend any other wood alternatives as I am not sure how easy/feasible these wood types will be to source in New Zealand (Plans are form the states).

I'm not really going to be much help on that one as I have never worked on boats. As I am not sure of where and why those woods indicated are used on the boat, and if they have a specific function for their placement.
Best bet would be to talk to a local wood supplier and see what kind of alternatives you would be able to find more easily.

I'm looking at sticking some wood (ash) together with some form of adhesive as part of a university project. The bond strength needs to be around 0,05MPa. Can you recommend an adhesive which I could use for this?
Cheers.