2 meetings is fine but not the customer meeting. You should provide a written or video reference that you can reuse with everyone.
If your customer would normally be open to do a call, you can record a diligence call with the customer and give your small check investors access to the pre-recorded call instead of a direct call w/ the customer. Explain that for checks less than $500k (or whatever threshold you want to set), you aren't at liberty to give access to your customer as your customer's time is precious.
Now, if you have a larger VC that's interested in talking to the customer, you can ask them if they are ok having the customer diligence call recorded that you can use for others. OR, alternatively, you can tee up a bunch of questions and have your customer answer them and give the recorded call to the small check investors. Here's a list of standard customer diligence questions. Have them record answers to these and share them with small check investors that ask to speak w/ them.