These are just my opinions, and they are probably all wrong, but this is how i'd do things:
1. How many whiskeys should we try to taste at a session? (1 oz?)
6 is a comfortable number, any more and your guests will be too sozzled to care about what you are serving up.
2. Should we include something to eat between/during?
The tastings i've attended have a plain oat biscuit on the table, and plenty of water. I don't think any other food would really be appropriate.
3. Suggested first time tasting malts?
I'd suggest something pretty basic, along the lines of:
1. Bruichladdich 10 or 15
2. Strathisla 12
3. Highland Park 12
4. Benriach Curiositas
5. Aberlour a'bunadh
6. Ardbeg 10
I think the above 6 would be a fairly good intro tasting, and most of those bottles can be had for reasonable prices. How long have the people attending been drinking whisky? If it's a more seasoned bunch, i'll see if I can come up with something a bit more interesting.