I work at an insurance company and am pretty familiar with this product.
Nearly all term insurance policies sold over these exchanges are "level term" meaning they cannot increase the premiums over the "term" of the policy (often 10, 15, 20, or 30 years). This is typically the lowest premium way to buy insurance and I agree that it makes sense to have some coverage when starting a family.
I assume that cash refunds refer to a fairly recent product innovation where there is some "surrender value" when you "lapse" a policy (sorry to keep quoting stuff, but insurance talk tends to be pretty jargony). In general, these policies costs a little more and my feeling is that I wouldn't pay for the additional liquidity - I wouldn't buy for a longer period than necessary and so there wouldn't be a need to lapse.
BTW, I think that going about this purchase via an online exchange makes a ton of sense - cheapest price should win (for other policy types, the strength of the company becomes important, but this is not too important for term as the features you are interested in are guaranteed) as there is a backstop for insurance policies akin to the FDIC backstop for banking deposits.
Hope that helps - MathNinja