Thanks the replies, really appreciate all the tips.

I am thinking about limiting the options to the first PHB (for starters anyway). And for ease of reference there's this:
Offline Compendium
Interesting, I hadn't seen that one. I think, as with all the compendia, you kind of still need to have the books and such to reference in order to understand how things work. I mean, a power may be self-explanatory, but in a lot of cases there is 'other text' that one needs or should have for reference.
Also as mentioned in my post, we'll be using Roll20 and the sheet there seems serviceable, also I have been creating macros for some of the first level powers.
Regarding combats being slow, I do have the errata the WotC team did, and I can see they modified many monsters by doubling their damage output and halving their HP. So this is something I am aware of. It is pretty crazy though, that such a thing slipped past their playtest. Oh well naughty word happens
The standard damage expressions were increased, and then most newer monsters were written (or sometimes they were rewrites of old ones) to ACTUALLY output damage that matches those expressions. It is far from being 'doubled' however. Baseline damage as of MM3 grade monsters is about Level+8. If you look at MM1, damage rarely even reaches the official Level+5, and things like restricted damage and increases for things like brutes which the DMG called for are almost never present. Now, if you get into higher levels, then yeah, some of the MM1 damage was half what it should be.
Likewise there were no changes in hit points in MM3 for monsters. The only change happened a bit earlier, in MM2, when ALL solos were reduced to 4x hit points instead of 5x, a 20% reduction. MM3 does rely less on brutes and soldiers, and doesn't have as high a proportion of elite/solo monsters. Those factors tend to cut back on 'grindy' monsters some. Also monsters overall design is much better in MM3, their powers synergize with their designs better, there are many fewer cases where monsters just bog down play, etc. It is definitely best to stick to MM3 and MV:ttNV where possible, but most older monsters are OK if you take care in building scenarios and do the adjustments to their stats. It is certainly NOT necessary to do drastic changes like cutting all their hit points in half!
Anyway, I'll see how it goes. We like 5e very much, so if this 4e experiment turns bad, I have a some great 5e stuff lined up
PERSONALLY I think 4e is best approached as a narratively focused game instead of being played in a 'classic D&D' mode, perhaps even play it 'zero myth' if you want, but then you would probably want to give the players a lot of chances to fill in world details. Anyway, the game really plays best when the action is very highly charged. Something that plays like a cross between D&D and Indiana Jones is best. If the building isn't on fire, or the roof falling in, or a wagon racing out of control towards a cliff, then you probably should be 'skipping ahead to the interesting part.' Say 'yes' a LOT, and really consider using SCs, but do them right. If you have any WotC supplied adventures, ritually burn them before you start play and never ever use them! I've heard that a few of the later ones have been considered 'good', but I'm skeptical for the most part...
You can run the adventure in the back of DMG1, Kobold Hall. It is too short to turn pear shaped, though it is still an example of what NOT to do for the most part.