What a guilt trip... and I mean that in the nicest way possible!
Have the child if you wish and can afford to clothe and feed it, because you obviously have the other gear you need (I'm assuming you kept your #1 package of stuff?)... diapers (not if you did cloth), wipes (not if you use moist Viva paper towels or soft moist cloths), formula (not if you're breastfeeding), childcare (not if you're already at home)... you get the picture:)
Have the child now, because of the additional time it will take out of your potential earnings without overlap. For ex: Your 3 yr old goes to school in 1-2 years and you have the potential to work part-time, but you waited to have #2 and start the cycle of SAHM again for another 4 years. Versus: you have your child during/near overlap, and have around 3-4 years more of potential part-time employment, paying your parents sooner. Also: how old are you and will you be physically capable of getting pregnant?
So, bottom line: do the math for all scenarios, projecting 3-5 year goals. If you can afford those added costs while SAHM and either put payoff on minimal or hold, you might net more income long-term than if you wait short term. PLUS, why only look at what's going out -- look at what you can get coming in or what you can cut/rig/revamp to get more coming in:)
Best of luck to your family!