Well, first off - chat with your homeowners insurance about it....they are huge insurance risks...much like pitbulls without manners.  If you have a pool, they won't insure you at all.  (according to my insurance, anyway.)  Secondly, if you do get one, invest in a fence to keep the kids from falling, bouncing, or flat out flinging themselves off onto the grass.  I personally would love to have one of these - and really enjoy playing on the trampoline type things at Pump It Up when I take the kids for parties or pop in and play time.  However, the idea of stitches, kids and broken limbs, blood, or serious head/neck/spinal injuries as a result are enough to keep me from letting the kids near one without a net/fence to help protect them. 

If you do get one, make sure you have the fast route to ER or Urgent Care mapped out...my kids have enough fun climbing trees (too many scrapes, cuts, bruises to count),  pulling each other around on blankets (1 trip to ER for CT scan with youngest), jumping off ramps with their bikes (lots of blood, gravel in the knees that had to be cleaned out before infection set in), and many other "accidents" which have led to calls to poison control (windex sprayed in the eyes, soft scrub rubbed in the eyes, etc.), eye doctor (oldest poked the youngest in the eye with a washable crayola marker pen....nice expensive trip to the eye doctor for eye ointment - it was only a small scratch on the cornea).....get the point?  I have enough trouble keeping the kids safe from their "fun" and folly, the trampoline would certify me insane!  

My other suggestion, find friend with one and let the kids try it out....then make the decision.  Let us know what you guys decide.        

We have one and b/c of homeowners insurance are required to have a fence around it.   Watching the kids play on it, and also recalling how many times my siblings and I inadvertently flew off of trampolines as children, I'm a big supporter of the trampoline/fence combination.  I really love having the trampoline...the kids (and I) have a lot of fun on it.  It's a great energy release for them, and it's great exercise....builds strength, balance and coordination.  There are occasional mishaps (but isn't that the way w/ any physical activity involving kids?).   And there would be less mishaps w/ only 2 children on the trampoline at a time (as opposed to my 4). 

Also, the rectangular trampolines are actually safer for multiple jumpers (everyone doesn't converge in the center), but i don't know if they come w/ fences or how they compare price wise.

Trampoline, I would consider anyone without one (or limited access to one) an irresponsible parent. Placing your young children haphazardly in harm's way is the right of every parent, as well as the right of every child. Childhood isn't about living in a padded closet. Childhood is about the times in life that real adventure is experienced and its many scars, which latter displayed with pride, flesh wrought trophies to your friends and children whilst recounting stories of summers past. Insurance be damned. Bring on the fence... it only makes it funnier.

We had to leave our trampoline in Oklahoma, and it is one of the most missed items by everyone.  I highly recommend one!  Firefighters and EMT friends would never let their kids on it, though, because of all they see, but we never had an injury, and the kids were on it all the time, including David, from the time he was crawling!  And, we did not have the fence around it, though we probably should have.  We just watched them, but I have to kind of agree with the previous comment by noahj.  When we were kids, there were no bike helmets.  We didn't wear knee pads when roller skating.  No one I knew, who had one, had anything around their trampoline.  But we didn't wear seatbelts or use carseats, either, and I wouldn't give that up now, so I think the safety measures are good.  They certainly can't hurt!  Good luck making the decision.  If we had the backyard that you have, we would definitely have one.  However, I never knew it was a problem with insurance - never heard that before.

We would definitely get the fence.  That was already a part of the proposed plan.  My kids have been on several at friends houses and it's hard to get them off.  I would actually get on it myself, too.  I miss that from my own childhood, and it's some good excercise.  We already know the quick way to the ER.  Both kids have been...  Holly had a dislocated elbow and Layton got Stitches in his lip.

I also think that kids should be learning their physical limits when they are young.  It doesn't take them long to know what they can and can't do.  The injuries come from the "childish" decisions and attempts they make while KNOWING their limits...  and those decisions are going to happen with or without a trampoline in the backyard.

So I think we are decided on getting a trampoline.  I certainly would not want to be irresponsible and NOT have one!  (Thanks, Noah!)  Are there any other safety suggestions?  Brands?  Good rules of thumb?  I appreciate everyone's input.  Thanks!

And Becky, this is a possible Christmas gift, so don't say anything to Layton and Holly...  or probably your kids either...  just in case.  :-)