"They also proposed a budget of $5,000 which without being able to do the above is unrealistic. I would have to charge that much based on their creative and SEO needs. If I can justify the expense of the above I believe they will increase their budget."

The question on the budget level is by how much, the quickest way to knock out what they want would be to buy in a number of solutions and then nail them together behind your design- and that ain't as easy as it sounds and it doesn't sound easy.

The question I would ask myself is whether it is worth starting or not. Sometimes as both a client and a builder I think that straight forward "This is what I can do this is what I can't" is much more rewarding, especially if you know a (wo)man who can do it- its an old word but demarcation has its advantages, as does collaborative working- the people you kick business to will also kick some back.
pete