There are some companies that do what you ask, they`ll tend a grave, clean, put flowers on the grave & weed etc for you & will take Photos to email to you.
Whether they have similar in Belfast I don`t know?
However most cemeteries have strict rules on what is/is not allowed & its well worth checking this out first. You will almost certainly find that you`ll need to be the owner of the grave or have written permission from the owner before being allowed to do anything, as far as I know this is pretty much a standard rule, however leaving a bunch of flowers is unlikely to cause a problem.
However I wish you well.
Regards.
Steve