Whilst I don't have any legal knowledge, I'm in the process of trying to unravel problems with some land in trust that ripple back to things not being done properly when my grandad, dad and grandmother died...
So make sure the trust clarifies exactly what happens if somebody dies - horrible to think about I know, but pretty important and for us, it's causing lots of problems and heartache years down the line. On the other hand the solicitors seem pretty happy - which is double galling given they are the ones that screwed up in the first place and are now getting paid to unscrew 

We've also had a problem that for one bit of land a beneficial interest passed down to my mum through my dad's will. Not had to do anything with it, just knew it was there and that we owned a chunk of it. Discovered recently that when the other co-owner died, they left their share to their wife and a beneficial interest was noted in the land registry documents. However when she died, it was all left to her children, no mention of the beneficial interest and they now believe it just belongs to them. Solicitors are adamant that this is impossible, that we must have signed away the beneficial interest as it's not possible to transfer land ownership/rights without both parties signing. However why would we do that - we haven't ever really discussed the land with them, there's been no need and why would my mum decide to give stuff to my cousins when she is adamant that she gave her share to us. Very strange. And pure fluke that we found out there was a problem when we did - why would you go and randomly check land registry documents for land you own when you haven't done anything with the land. You carry on living in your house - you don't suddenly discover one day that somebody else has decided to register it in their names because they felt like it.
So I guess I am saying that you need to make sure the trust document is tied up properly but also make sure that you make specific reference to it in your wills and include in them anything you want to happen to it, so that it doesn't all go pear shaped when one of you dies. 1, 20, 30 or more years down the line, it is very difficult to remember what happened precisely and who has what share of what. if there is a copy of the trust document with your wills and it's kept up to date if there are any changes made it will make things much easier for your grieving relatives!
Good luck!