To keep it simple: interest rate 5%-10%, 10%-50% discount, 2 year term, and a cap of 2M-3M for the first guys. These ranges are totally acceptable by all investors(if they actually know what they are doing). I recommend 7% interest, 20% discount and a cap of 2.5M.
For the second stage guys all I would do is change the cap to 4M-8M dependent on your traction. By only changing the cap, it keeps all the terms understandable for everyone.
At the end of the day, if you are a hot company, growing, with a sustainable business model, you will get funding easily and it will be on your terms. Really focus on getting that beginning traction. Treat the cap as a way to avoid that discussion of valuation today but to accurately compensate your early backers immensely when it takes off.