A $4000 budget for elopement is plenty.. if you are looking more center-strip then consider Planet Hollywood or (less expensive) Imperial Palace. Both are sufficient and not horribly expensive.
A word of advice - unless you want to drop half your budget on photography, then do NOT use ANY of the chapels or casino chapels. Most casino chapels you'll pay $1000+ just for the disc of images. Expecially stay away from any chapel that uses Cashman, as they are difficult to work with, hard-sell, and way overpriced.
Have you considered an off-strip ceremony -maybe up on Mt. Charleston or at a nice local park? Many vendors can package officiate, transportation, photography, etc. for a reasonable price -probably less than just the purchase of your photos.
We're doing a wedding for a couple in October at the top of Mt. Charleston, the location overlooks the back-side of the mountain with greenery for a mile or so, then beautiful reddish desert and mountains as far as the eye can see. At sunset, the mountains in the background GLOW with firey red.
Disclaimer: Yes, we are vendors, and yes we can provide these services - but what we post is FACT. We see brides being over-charged every day by the chapel's photography services.