Personal watercraft is no longer limited to the stand-up kind of jetskis. They have 2 or 3-seaters that are stable and a lot fun. The learning curve is minimal so everybody can enjoy it. Children under the age of 14 should not be driving and from teenagers should only be allowed to drive under close adult supervision.
To get away from it all but still have the amenities of civilized life (kitchen, refrigerator, satellite TV, even a jacuzzi hot tub) then a houseboat rental may be for you. Lake Shasta has a lot of companies around the lake that can rent them out from a weekend to weeks. Most houseboats have a flat roof so you can pitch a tent up there for added accomodations. While not exactly known for speed (most of them go about 10mph), they are stable and fun for large groups. After you load up at the marina, you have a lot of coves & inlets around Lake Shasta to choose for your mooring point. Most places where you rent the houseboats also offer other watercraft rentals: ski boats, jetskis aka PWC (personal watercraft).
Kayaking has such a low environmental impact that it's a wonder not more people are doing it. It's also great exercise for the upper body and especially the arms... so easy even a child can do it! You can bring your own kayak to the lake (these in the picture were bought from REI - approx $230 and the oars were approx $65) ore ven rent them from several resorst around the lake.
Holiday Harbor Resort at 1-800-776-2628 (www.lakeshasta.com)
Jones Valley Resort at 1-800-223-7950
Sugarloaf Resort at 1-800-223-7950
As when driving, be on the defensive when boating in Lake Shasta. Due to the large number of visitors who are able to rent any variety of watercraft: from kayaks to jetskis to houseboats, you need to be aware of the other boaters. If you're on a jetski or a small boat, do not cross in front of other boats or travel too closely in their wake no matter how much fun it would be to jumpt the waves. Always leave a safe distance between you and the other boaters.