volcanic activity

Why should you cancel? You may or may not have to change your programme depending on where you are going relative to the volcano and you may get stuck in an airport, but there is probably more risk for air space east or SE of Reykjavik closes - like over Scotland or Scandinavia than Keflavik airport

This is regular stuff. You never know, maybe you'll be able to see something spectacular, a "good tourist eruption" as they call it. When Bardabunga erupts, as it does quite often, usually the worst that happens is that a glacial flood washes a bridge away on the southern ring road, (floods can also go northwards) but the flood usually only runs for a couple of days and then some temporary road can be put in place. So whilst it might make somewhere you wanted to go to temporarily inconvenient to access, there is the rest of the country. Eruptions like that one that caused major aviation disruption a few years ago are relatively rare, and such widespread disruption hasn't happened with previous Bardabunga eruptions, although there maybe some local aviation disruption from it.

Of course it could be much worse, but that would be unlikely.

was doing Fimmvörðuháls, have heard there is earthquakes, could this prove fatal on the mountain pass?

hi, have people died on these mountain walks in previous eruptions, and how long was the warning in place last time before it went off? are earthquakes widespread or just around the creator?

was doing Fimmvörðuháls have heard there is earthquakes

They are little tremors and quite a long way from there.

But in any case, to ram the point home since you don't seem to have got it yet, you don't actually know if you are doing Fimmvörðuháls. This is because, given the time of year, and the general weather issue with walking this pass
(1) you need to ask at the time whether the pass is still open to trekkers - heavy snow can close it for the season as early as late August
(2) if it is open, whether the weather conditions today are likely to be conducive to a person of your experience walking over it, issues can include strong winds and very poor visibility, which given steep drops matters.

There is a BBC TV programme around in which Julia Bradbury walks the pass at the end of August and gets rescued from it because of weather. I think it may be on you-tube. She came back a few days later in a helicopter and the weather was beautiful.

I said all this recently. Please go and do your research before asking more questions.

have people died on these mountain walks in previous eruptions

OK, to be clear, since you can't be bothered to look at a map and see what people are talking about, F...hals runs to the west of the large icecap Myrdalsjokull. The current volcano which is shaking is Bardabunga which is under the NW corner of the very large icecap Vatnajokull, which is separate from and some distance to the east of Myrdalsj. Tremors are localised to Bardabunga. It is not close to F...hals. There are locations much, much closer to Bardabunga, which are still open.

hi, have people died on these mountain walks in previous eruptions, and how long was the warning in place last time before it went off? are earthquakes widespread or just around the creator?

No, people didn't die because of previous eruptions.

The rest of the answer http://en.vedur.is/earthquakes-and-volcanism/earthquakes

There is nothing you should worry about except getting stuck in your virtual worries about some news :)