We put our kids in a tent by themself a few years ago - we only had 2 small tents to sleep in at the time (both borrowed). They were both under 3 years old - but the door of their tent was against ours... we actually moved our tent against theirs, after they were asleep in theirs, so that they couldn't get our of theirs without stepping on our & nothing could get into it without stepping on ours.
We were also w/ a huge group of people... eventhough we don't boat, we were with a boating group & they look out for the little ones, kinda like tribes use to. My father-in-law boats & we are the "shuttle bunnies" (get the cars to the take out while they are all on the river) when we go. But we get a free trip to the mountains out of it - so everyone is happy.
The kids did really well, eventhough it was their first big camp out... since then my father-in-law got us a big tent that we can use that holds upto 8 people. So, the last trip we went on last year - we had the 3 little guys sleep w/ us. The now 6 & 5 yr olds (the babies we had before) really wanted to sleep in their own, but we didn't bring the little tent, so they couldn't... the baby (now 3) wouldn't have been able to handle being w/out mommy - but he is also a momma boy & doesn't like sleeping anywhere unless it is his bed or in mommy's arms. So, I think that is more a different issue... he also won't sleep unless he has on a pair of pants & t-shirt. Things are a little different with him, but he's a cool little guy :)
Just play it by ear, see how things go - they will let you know if they can handle it or not, and have fun - if you all end up in a small tent... you all might stay a little warmer - lol.
Have fun on your trip!