Cruel To Be Kind? :/?

The explanation is kinda long so excuse the bullet point system:
1) My friend’s boyfriend has recently introduced his own friends into our group to ensure he spends as much time with his girlfriend (my friend) as possible. A few days after this introduction (which I missed due to family issues) my friend told me that her boyfriends friend called Jake had developed a crush on from looking at my facebook profile picture. My facebook is private so only my display picture would have been available to him.
2) I denied it asking how someone could have such an ‘intense’ crush upon someone simply from one picture, however my friend said to accept him on facebook seeing as either way he’ll be in our group so i’d have to at some point. However from the night since adding him, he has always popped up on chat making conversation. It soon became apparent that as nice a person as he is we have nothing in common. He then began to like and listen to all my favourite bands to make conversation. I told my friends that for me there was nothing that could develop into a relationship however they said people come across differently over facebook and to give him a chance and meet him face to face.
3) We all went as a group, and he was so painfully shy he only said ‘hello’ to me and gave short answers that couldn’t be worked with when asked questions. I was 100% sure at that point that we’d have nothing beyond friendship as i’m quite a bubbly outgoing person plus physical attraction was also absent.
4) I planned to tell him face to face the next time we met (not over facebook as I view it as a bit disrespectful) that I only liked him as a friend as he had been grilling my friends for info on me, plus I in no way wanted him or anyone else to think I was leading him on enjoying the attention. However I live in South east england with my grandparents based in Scotland, and my Nanna fell ill and died. It was a short yet also long and personal struggle that included each member of my immediate family caring for her causing a deep impact on us all as she died. Whilst in Scotland dealing with things, Jake (who is very comfortable with money) suggested that I sell all of my nanna’s possessions for extra cash. I got annoyed as we aren’t hard for cash, plus of course being close to a relative you have your own self-worth on their items.
5) This second meeting occured about a week after the funeral, however I drank whilst (stupid as it sounds) forgetting that I was on antibiotics with me ending up in hospital crying to my parents about my Nanna of who I clearly wasn’t over and I failed to talk to him. As a result of the drinking I was grounded for two months, again I wanted to do it face to face, however when my grounding was lifted he went away to America for two weeks before I saw him again dragging it on. He’s now back, and has bought me some presents for which I’d feel awful for accepting seeing as having told a friend that he plans to ask me out when he gives me the presents to which of course I want to decline. We all went out a week ago, however his friends got drunk and kept making lewd jokes and never leaving his side making it impossible to take him aside quietly and tell him.
Although it’s disrespectful, and I feel a coward, i’m planning to tell him either tonight or tomorrow on facebook chat about how I feel – just wanting to be friends. Tuesday we’re all going to a theme park, where he plans to give me the presents and ask me out, the reason i’m turning to facebook is because if that were to happen, me turning him down there ma create and uneasy atmosphere between us and possibly ruin everyone else’s day as a result.
So basically, does anyone have any tips on what to say to him which would hopefully mean we remain friends?
Sorry this is so long, any help would be greatly appreciated