Hi, Matt here and I'm looking to help you for your project.
Please expand "Converted spreadsheet should be interactive with calculations.". I would create HTML5 converted table with interactivity e.g. sorting by columns on click, ascending and descending switch and some row highlighting etc. So no formulas entering, editing and parsing (calculating) possible.
Full Excel embedding is of course not possible without server side technology that would allow it (if it all, older ActiveX control with embedding spreadsheets on the web page - never did that, sorry - or using Java libraries, there is one from the authors that write spreadsheet handling part for Microsoft). My bid is not for that.
Looking forward to your reply,
Matt