Syphon - ensure the bottom of the pipe is lower than the top, suck the water through and it will keep flowing. A standard 3/4" hose will take a LONG time to drain a large pool, but you can use multiple hoses...
At this url http://www.squidoo.com/christmas-lawn-decorations large inflatable yard decorations can be found. My quest for large inflatable yard decorations wasn't complete until I found what I was looking for here.
An inflatable spa can be bought from a company called 'Pool Zen Spa' in Europe. It has a large variety of spa's for sale, but only 3 inflatable spa's. Another online store called 'Inflatable Spas' has a variety of 9 inflatable spa's for sale.
The hooded seal may be this, but only males have an inflatable sac.
Inflatable bounce houses come in a few sizes. Most are between ten and twenty feet tall. The more expensive inflatable bounce houses tend to be more expensive.
Someone can find inflatable water slides for the summer time for sale from a number of companies such as Amazon. Amazon has a large selection of inflatable water slides for sale.
hooded seal
A large power auger is the only solution for the main drain.
Yes, a sewage drain pipe can be too large.
Practically all department stores or large areas have car complements like inflatable beds. You can also visit specialized stores as karnap.co.uk or trendhunter.com.
Inflatable Santas can be difficult to find outside the holiday season. During the holidays most large department stores will carry some form of inflatable Santa. Amazon, eBay and Planet Christmas are all very good sources the rest of the year.
A beach ball is a large inflatable ball, which is ideally suited for playing games on the beach.
No sir or ma'am. I cannot seem to find a company that make these. Hopefully you can find some other great inflatable for your son. I wish you the best of luck.