Gary,
On a shallow lake with a fixed keel, in time you are going aground. If your lake does not have rocks or a hard bottom, most of these groundings will be of little consequence, other than you have to get yourself free. The advantage of a swingkeel/dagger board, of course, is that you pull it up and go another way. With the fixed keel, it's going to be a different technique. I sail in a shallow, but large river in NC. My current boat, a 32 footer with wing keel takes a different technique. But I am assuming that your fixed keel does not have a wing or bulb on it....if it does, please so state. First of all, to take lots of stress out of the situation, make sure that you have a working depthfinder on your boat and verify it is accurately set (you do this by actually intentionally touching the bottom very slowly and measuring the depth at which you touch bottom...if the depthfinder reads different, adjust the depthfinder, or make a mental note of the reading number that was displayed when the bottom was touched. When you sail, keep close watch on the depthfinder. When the readings start to approach that number, slow the boat so that if you hit, it'll be easier to get off the bottom and turn away back towards the deeper water.
When you do get stuck, a technique that I used was: To get off, you want to twist the boat around and go back off on the recipical of your original course (i.e. the same way you came on). First determine how the wind is acting on the sails. If the wind is trying to drive you further aground, drop the sails. But many times the wind will help drive you off after you twist the boat around and "tack the sails". Start your engine and use that in combination with the sail to drive you off. Work the rudder back and forth as you motor and this will help break the suction forces between the bottom and the keel. If you have crew on board, have them (with life jackets in case one slips in) go to the shrouds and swing their weight over the side...feet on the edge of the boat, hands holding the shrouds. And if they can rock the boat from there, that also helps. Their wieght and the wind forces should heel the boat over, giving you a few inches of reduced draft, which is all you will normally need to get the boat free. If this doesn't work, you may need to place an anchor over the side with a line attached to a halyard so that the boat may be winched over more on it's side. But if you don't have a dinghy, this means someone has to go into the water, which could be problematic if the water is cold (i.e. risk of hypothermia). Float the anchor out on a fender or lifejacket. When the anchor line/ halyard is tightened and anchor sets, the pull will be against the top of the mast and will use the mast as a lever arm to heel the boat. Once heeled over, you can motor off. Then, you'll have the problem of recovering the anchor....you might attach a float marker and come back later in a shallow draft boat if it's not practical to do from the sailboat or your dinghy. Often, if you are alert, before you ground completely, you'll feel a couple of easy bumps...then you turn immediately and often you can retreat the opposite direction without ever coming to a complete stop.
An additional technique to heel the boat is to attach a weight to the end of the boom and swing it out...that weight could be a bucket or water bag filled with water, or one of the crew.
Don't be intimidated by the larger boat. I find that my 32 footer is easier to sail and handle that my 22, 24,28 footer previous boats. Docking/undocking is the only thing that is more difficult.
As someone else said, spend some time with a shallow draft boat and depthfinder finding and recording on a chart (if there is no chart, make a hand drawn one) where the water is shallow.
Tell your friend, not to worry, if you go aground, you, not him, is responsible. After all, you are the captain and the owner. Tell him that you need him to help with docking, setting and adjusting sails. And especially, to use as moveable ballast in the event you do ground....i.e. he's the guy to swing out on the shouds at the beam to heel the boat above.
As a precaution, the first few times out, you might alert the dockmaster at the marina or other boater that you might need for them to send out an assist boat and make such arrangements in advance. Contact them by radio or cell phone if you need assistance of a power boat that can pull you off if above techniques fail.....but I think you will be fine without their help using the techniques I mentioned above.
Good luck, enjoy your boat.