Water in the carburator?

I have a Toro mower that was new this spring. It has worked great all summer up until now. I do use the additive to the gas to make the mower start easily ( on the first or second pull). I just added the bottom inch or so left in my gas container and now the mower will not run. It will start but will not run. On the first start it ran for about 2 minutes or so and I started mowing before it died out. On subsequent starts it dies after a few seconds.
The fact that it ran on the first start makes me think that there may have been water in the gas that I added. I did check the gas container to make sure there was no settlement in the bottom. I live in MS so it is very humid here and the can sits outside. I have had this problem once before with a mower from Sears. At that time I had not added any gas. Upon having that mower serviced the carburator was the problem as it did have water in it. I would like to know how I can avoid this problem in the future and how I can clean and dry the carburator assuming this is the problem. To me it seems the likely answer.
I am a 65 year old woman so I don't think I can take the carburator off and clean it? My son could if he had instructions on how to do it. Should I replace the plug and filter even though this was a new mower and has not been used more than 10 times or so?
Going for repairs is getting to be expensive! Thanks for any help you can offer -
PS Could I dump all the gas in the mower and add new and keep starting it until the fresh gas gets into the carburator? Would that get the water out of the carburator - assuming this is the problem? Or could I spray the carburator with something that would dry it?