Thanks to everyone who has replied. I too am a bit nervous of all the things that 'could' happen. I think I will contact SIDS and see what research has been done in this area.
Saram, how old was Ari when she went in with your son? I have a friend who put her kids in together when the little one was about 6 months and they loved it too. Nice to have company for both of them.
Thanks,
Megan