I have a 250 and I was really happy with it wheb I took it to the beach. I dug everything but I could tell you with certainty when it was a bottle cap (my wife uses them for craft).
-as for stability I don't know your beach conditions but I was able to use it in the wet sand and water. I discriminated the first 3 notches so iron, foil, and just below Nickle. One of the times I pulled a penny out of about 3" of water 7" deep on the sand. I am using a nel coil though.
-there is a good thing that I can see with going with the 250 is that you have the option to get a large coil to cover more ground. I was using a 13x14 dd coil and I was covering a ton of ground each time. I know the f2 has coil options but the ace has a wide selection between garrett and aftermarket if that matters to you
As for stock coil I get dimes and nickels 7" penny's at around 8" coppers slightly more. And quarters are just shy of 10"
The ace 250 or 350 is a deeper machine
The ace has 12 notch discrimination and target ID while the f2 has 8
More coil options for the ace.
Both have 8 sensitivity settings
The f2 has a 1-99 target ID number which the ace does not. This is really nice and is what I say evens the field on both detector making them a good choice either way.
Being that your son is 10 I would say go with the ace because the controls are slightly better labeled and layed out where a 10 year old would have an easier time working.
Second reason is because the ace has modes which you can push the button and go through preset discrimination such as coins, jewelry, relic, and custom. Which would be easy for a 10 year old to look at and change to look for coins.
Either way they are both really good.
I wouldn't way much on the fisher pinpointer. I have no personal experience. and could be wrong but everything I have read they are about worthless.
Also might consider the 250 over the 350 where as the 350 comes with the larger dd coil for about $80 more. If you are hunting more coins then relics the 250 has more notches dedicated for coin and jewelry targets. The 350 has more notches for iron if you would be relic hunting . Sorry I don't want to add more confusion most people don't realize that.
As for the Teresos I have heard really good things about them but being that he's 10 he will probably benefit from something with a screen.
Hopefully fisher fans wouln't give me to bad of backlash because I think they are equal but I recommend the ace with the age probably not going to take the time to Really learn the TID numbers combined with the simplicity of the aces operation with control layout and mode options I think it will be a better experience.
