The better approach is to separate your web app and marketing sites. Your marketing site is yoursite.com and your app can live on something like app.yoursite.com.
There are lots of marketing stacks that include all the tools for making landing pages, integrating them with advertising campaigns, etc. Don't hinder your marketing team by not letting them use standard marketing tools.
If you really want to stay on the same domain, I would still separate things into two separate stacks, but put a reverse proxy in front if it. For example yourdomain.com/app can proxy to app.yourdomain.com.