I would highly recommend roof vent covers...IF it's raining, you can open your ceiling vents and still have air circulate....Most leave the roof vents open when 5er sit's to help "air out" and help keep a little dryer inside..Don't know that it necessarily makes it any "cooler".....but hot air will rise and if vent is open, it'll go out the vent...Cost isn't much and install is simple..well worth the cost.
LED lighting, it's your call...I've not gone to it yet, but possibly will in the near future...Only drawback I see is initial cost is pricey....but well worth it in the long run, if LED lighting lives up to expectations...I like the looks of them and again, eventually, I'm going to convert to LED lighting.