I Amsterdam Card & Transport to Keukenhof Gardens

Yes I Amsterdam Card, would cover a tram/train/bus to travel to & fro Keukenhof Gardens
You have lot of options on how to get there
https://keukenhof.nl/en/plan-your-visit/how-to-get-there-copy/#By%20train%20and/or%20bus

There is normally a Keukenhof Express that departs from Damrak 34
But double check with the concierge.

Thanks a lot for your prompt response!

One final question:

As indicated earlier, we are staying at Best Western Premier (Delflandlaan 15, 1062 EA Amsterdam) and plan to visit Haarem, Keukenhoff, FloraHolland AalsmeerLeiden, Huge Rotterdam & places around Central Station. Would GVB Card work in these places and in surrounding areas?

Thanks!

I don't see anything about the Keukenhof listed in the Iamsterdam brochure. I do see in bold print

Transport outside Amsterdam and NS train
travel are not included

So you will need to get an OV Chipkaart or paper return train/bus tickets to see anything outside of Amsterdam, which I am going to assume is only zone 5700.

You can look up prices, at least if you get the Chipkaart and load money onto it at:
9292.nl/en

At the Keukenhof Gardens website you can buy a combi ticket which includes admission and the cost of the bus ride to/from Schipol Airport to the gardens. This would negate the need to get an OV Chipkaart. All you would need to purchase is a rt train ticket from Centraal Station to the airport which is easily done.

Another post by the OP also asked about trips to Haarlem, Leiden, FloraHolland Aalsmeer, and Rotterdam, so a Chipkaart would be handy making several journeys.