I've never been able to say my 'r's despite years of speech therapy and elocution lessens. When I was very yound, speech therapy helped, and as I was older, elocution and speech and drama helped a lot to make my speech clearer.
Not being able to say 'r' isn't really a problem in England. But it's a big problem in Belgium where I live . I speak flemish fluently and can spell everything, I just have a huge problem pronouncing any word with an 'r', making it hard for people to understand me. I need people to understand me for my profession, and it makes it really hard. Also my name contains an 'r' and people here can't understand me when I say my name - again, not a problem in England. I would never choose to name my children with a name with an 'r'.
I would certainly recommend speech therapy. The sooner these problems are sorted the easier.