In reply to Yanis Nayu:
Assuming neither of you have web development experience, you have a few choices:
1. Find a good small company who could choose the packages and integrate it for you.
2. Or, get a short list of products that look ok, and speak to the software house about someone they recommend to do you an implementation.
3. Figure out the budget and review. £500 (excel spreadsheet and facebook), £5k (minimally adapted package and payments) or £50k (reasonable but minimal bespoke implementation) will make a big difference on how to proceed.
Above all, cut the spec back to the bare bones for the first implementation - the minimum that will get the business running. Then spend money on marketing, design, and search engine optimisation. Run the business with that for a few months, and see what to do next.
Make staged payments, and hold back 20% to keep them keen on the final snagging.
Good luck!