Hi, we've just put the 12 ft version up! Our 2.5 yr old loves it, as do we ! It doesn't appear that small inside. I would think the 10 foot size is easily big enough for two kids (if not three!!).
It's quite reassuring that you can't get yourself caught in the springs (it's not impossible, just much harder than a normal trampoline). The actual footprint of the trampoline is larger than expected as the legs kick out (i.e. the 12 foot version has a footprint of about 13ft).
Both my partner and I had a jump on it together and we definitely didn't bounce towards each other as much as a round one.
Overall, I would recommend it and I actually like the fact it's black; despite being a huge monster, it seems to blend into the garden better than a green or blue one !