This information is from a few years ago but I believe you can have multiple accounts linked to your Credit Facility.

We used to own 3 retail shops and each shop had Merchant Credit Accounts.  Two of the shops had separate Accounts but the 3rd smaller shop was owned by the parent shop and was on the same Merchant Facility.

Two locations, same Merchant Facility.

I think you would have to open the Account in your own name and link each other "shop" to the main account.  A bit like linking all your ebay IDs to one paypal account if you like.

But it is a very expensive exercise.....you pay to have the account and to rent the machines and you also pay a fee for each card processed....anything from 0.05% up to something like 5%.  The smaller your turnover the more you pay % wise.