No, do not expose your wallet ID. That is used for logging in to your wallet on the site and is for you only.
Instead, simply expose your bitcoin address. Making that publicly available will mean anyone can send your donations and everyone can see the transactions happening with that address. There is no security risk in exposing your bitcoin address to ...
Googling this, my first hit was the blockchain.info website FAQ. Under the point "How do I make a public note?" they show the following picture:
I'm gonna go out on a limb here, but I think it means that you can put "Anything you like up to 255 characters." into a public note.