I really like Javea, although it has been many years since we have stayed there. We went to the main beach in town last summer and it was beautiful and perfect swimming for a 2 year old. Fine sand, long shallow bay. Here is a link for a rental, but I'm sure you can find many more.
http://www.ownersdirect.co.uk/Spain/s15.htm My favorite beach is Granadella, a rocky cove with a couple of Paella restaurants and not much more. You would need a car to get there, but it's worth it.
We've been going to Denia every summer for a few years because of friends there, but I think it is too crowded. Have fun!!!