This all depends on your kite size and your weight. If your kite has been suggested for you in normal conditions then this generally stands for a wind range of about 15-25 knots.

9.5 knots would be fine for body dragging and perhaps playing around with your water starts but you may find that you will get up slowly followed by sinking due to lack of power.

Generally most new kiters would struggle in these wind conditions because you need to sine your kite a lot to get going and that would be with a fairly large kite.

Keep in mind that the forecast isn't always right and even if you head down to the beach and chat with a few of the local kiters you may find this more valuable.

When I first began I tried to aim for days between 14-19 knots but it is better to be at the beach to see the conditions for yourself rather than sitting at home reading how sick it was on seabreeze

Probably be looking at a 10m or a 12m. I would tend to lean towards a 12m as we seem to get more lighter wind days in the 14-19kn range.

However recently we have had a lot of awesome days 20 knots +

My dad would probably be about the same weight as you and he uses a 12m fine.

Try to get a larger board when learning for the first couple of years as it will help with your progression. Onboard will give some good advice on what is best for a learner. If you are still unsure with the massive amount of info that you will likely get from the store then you can always give your trainer a call to clarify if the kite/board combination would be suitable before buying. Another option is to post in the newbie section with the potential options you have and see what people suggest would be best.

My recommendation is if you are buying second hand get the newest kite you can get for stability and safety reasons. Don't grab anything older than 2008

Since you are having lessons with Red Baron ask Guy about the best kite size for you. Your instructor is always best positioned to give you correct advice as to the kite sizes etc.. The guys at Onboard are pretty good too and they will be your second point of reference.
Other then that what Spawn said is more or less right - 10m is probably better once you're experienced, but it would be harder to learn on. 12m will have the power to counter your lack of technique - easier to get up on and easier to go upwind on.

As to the kiting in 10 knots definitely give it a miss. Unless the forecast changes (as it often does). You won't even find any kiters to talk to on the beach.

If you have some time saturday, the Windsup school will be down at westlakes beach (100 military road) from about 11.

At least there you would have some crew in the same situation trying to have a kite....