Dear Pollyi,
TechSoup and Idealware published a 2-part article called "Selecting an Online Donation Tool," which you can find here:
Part 1 and
Part 2. It's a few years old, so some of the vendor-specific information will have changed. But it should get you started. And here's a link to a vendor comparison chart from
Affinity Resources. Note that the charts has 2 pages (a link in the upper-right corner says Table Page 2).
I recommend looking for a system that will allow you to create multiple commerce pages. You will want one for general donations, which should be posted all the time. Look for a vendor that can handle tribute gifts and pledges, as well as any other special needs like recurring donations.
In addition, I would create separate pages for events and special fundraising campaigns. Make sure the vendor can collect the information you need for your event sign-ups, like guests and golf foursome members. You might also want a system that can issue receipts that distinguish between tax-deductible donations and payments (or portions of payments) that should not receive tax receipts.
As far as getting donations and event sign-ups into Exceed, you can certainly import the data. But you will need to deal with duplicate records, and make sure that the data matches your standards (e.g., complete information, legal zip codes, not all upper- or lower-case, etc). If your volume is low, it may be easier and more accurate to enter the transactions manually.
Robert