Getting from Varenna, Italy to the Bergamo airport
 

There is a group of us staying at Varenna on Lake Como for three days and then traveling on to Madrid on a Saturday flight. The least expensive seems to be Ryan Air. It leaves from Bergamo instead of Malpensa. How long would that take by a van service or taxi? How early would we need to be at the Bergamo airport for a 8:45 am flight? Thank you in advance for any information you could give me.

BGY is closer to Varenna than MXP. The distance is 65 km. For check in times, have a look at the ryanair website.

An alternative (unless your "group" is actually more than 3 or 4 people) could be to rent a car in Varenna for a day or two, use it for an excursion around the lakes district. And drop it off at Bergamo airport eventually.
Eventually, it may not be necessarily cheaper than a private transfer or taxi, but you would at least also get a day trip on your own out of it. More like a 2-4-1 than an actual saving, I guess.
Otherwise you find a link to one private transfer company on the airport's website: tourcarservice.com

For a Ryanair flight, it prefer to be at the airport 90 minutes before departure. They will not open check-in counters until 120 minutes before departure. And usually you will not know which counters they will eventually use for that specific flight so you can't even use any extra time to line up to be in the number 1 spot. So getting to the airport more than 2 hours before departure is useless.

>>>An alternative (unless your "group" is actually more than 3 or 4 people) could be to rent a car in Varenna for a day or two<<<

I'm not sure there is car rental in Varenna.

Most airport website list transport options. Check their site.

Wow! I am new to this forum and I am amazed at how helpful everyone is in giving suggestions so quickly. Thank you! We will have 10 people going from Varenna to Bergamo.

P.S. I am not sure if this has recently been changed, but in the past anyone not holding a EU passport had to see the Ryanair ticket counter first to get passports checked. Yes, it is a silly "only with Ryanair" experience.. check the airline's booking confirmation and website for their strict limits on cabin and checked luggage. And expect them to execute those to the max.