It's going to be tough to get into schools ranked higher than Babson given your GMAT -- it's below average & you are coming from a demographic that tends to have very high GMAT scores & is the most overrrepresented demographic among b-school applicants, which makes things that much tougher. I don't think it makes sense to wait another year since that will put you at 6 years of work experience, which starts to push you above the average at most schools. And it sounds like you've given the GMAT a good shot already so it may be unlikely to achieve a higher score next year.
If you've already got an offer & a scholarship from Babson I think it's worth accepting. You can always try to get more scholarship money, but that may be tough unless you can point to financial hardships (e.g. dependents who you need to support while attending b-school, medical issues that have resulted in high bills, etc) Congrats on the Babson offer & hope that helps!