Yes, they can. There are couple of ways to handle this:

You can create a ‘Family-visitor’ and ‘Staff-visitor’ account as a family and a staff. This is very easy but has 2 limitations – you will not know who exactly came and how will you provide the visitor password to them. The password, of course, can be set as simple as ‘visitor’.

On the other hand, if you want to know who the visitor was, then you can have everyone register. For this you can put a registration button on your website. The code for this button is just couple of lines, which oyu can give to your website developer. This code is given in Step 4 of the Settings page in iCare. The registration process takes just a couple of minutes.