This http://www.themodernantiquarian.com/site/1788 is a bit of fun and very close to Dalkey. Good directions to it from here: http://www.megalithomania.com/show/site/317
I've never had a problem at Newgrange. I agree with the others here though, Knowth http://www.themodernantiquarian.com/site/897 and Dowth http://www.themodernantiquarian.com/site/970 are musts if you are going to be in the vicinity. Have fun!
p.s. Vicster is a her, not a him. :-)