My son (also 2) has a head on the 99.9th centile (he was 97th centile at birth, but his head has grown - it's very rare to cross a centile in size so we had some hospital appointments about it when he was 6 and 10 weeks old - turns out he officially has familial big head syndrome, ie my DH and his family have big heads and DS takes after them!). He had a big head and a slim body and long legs.
Anyway, it was predicted via a scan at 34 weeks, during which the sonographer asked if I was planning a vaginal birth, to which I said yes, a home water birth, to which she replied "oh, with a head that size that should be interesting - good luck with that" 
. I was quite annoyed with her response at the time, but definitely not worried about my ability to birth him naturally (was practising hypnobirthing). I was induced at 42 weeks and ended up with an EMCS due to foetal distress, so nothing to do with the size of his head. After the birth, I asked the obstetrician about it at my 6 week check and he said that it generally shouldn't cause a problem during a normal labour (I didn't ask what constitutes a normal labour though!). Turns out one of my NCT friends had a son with a head on the 97th centile and she was the only one of us to have a normal vaginal delivery (with only a minor tear) - she had done hypnobirthing, had a water birth and had done perineal massage (she thinks all of that helped).
My DD was born 3 weeks ago and I had lots of scans with her, again showing a head on the 97th centile. She was also predicted to be big, and I was getting pressure from my obstetrician about my planned vbac - not about the head size (I asked specifically and she said it wasn't a problem - it was a different doctor from the one I saw after DS's birth) but more about the fact that I had gone so overdue with DS and the hospital weren't happy with vbac-ers going past 41 weeks (I had said I wanted to wait to go into labour naturally as long as it took).
As it turns out I went into labour naturally at 2 days past my EDD and had a straightforward birth. Turns out her head was at the top of the chart, but she was only 8lbs4.5oz - so the scans were right about a big head, but as I expected she had a slim body and long legs like her brother. I had an episiotomy, as she went into distress right when I was pushing and she needed to come out pronto, but my second stage was only 9 mins so it all happened quite fast. I've no idea if I'd have torn if I hadn't had the episiotomy...I've healed well, and within days felt physically totally recovered (the EMCS took me weeks to recover from properly). I also found the actual birth amazing, and really enjoyed the labour (compared to DS's labour and birth that is). I had done hypnobirthing again and found it really beneficial.
Sorry for the rambly post - am typing one hadned while feeding DD - but I think my problems first time around were caused by being induced (I had immediate hyperstimulation so had a pretty bad time of it - DS was also posterior, so back to back labour). Second time around going into labour naturally, and DD being in a good position, meant I had an easier time of it.
But your first birth sounds traumatic so I imagine you're considering an ELCS too. A friend had rotational forceps for her first and had a planned section for her second, as she couldn't face a vaginal birth again (totally understandably).