When your older kids are ready to move on to "older kid" type activities or trips, it's difficult sometimes towing a youngster.

ie. my older kids are of age and height to go on the biggest roller coasters at Kings dominion, but it's tough when 7YO has to sit and wait.

My 3.5 yr old DD loves helping with my 5mo DS but I will say that has been much more EXHAUSTING running after a toddler/kid through the last months of pregnancy and sleepless nights with the infant. I don't know that has anything to do with the age gap though.
As for the two of them, they get along fabulously but I will withhold final judgement until he is big enough to take her toys! And while I can see where people may think that European vacation won't work, we are entertaining the idea. There are ways to do it I think.
I'm not a SAH and I will say that the daycare bill is more than my mortgage but cheaper than if I had them closer together I guess. I CANNOT wait until the oldest is in K so we can afford to do something. Waiting another year wouldn't have been the end of the world.
Good luck!

My sister and I are 4 years apart. The biggest issue didn't occur to anyone until the later years, when my parents had to figure out who would attend which last day of school. My parents are still married but my father would come to my HS graduation and my mother couldn't. She was at my Sister's college graduation. True story. Growing up I wanted to do what my sister could do but I was just out of range. We were close enough for me to try and far enough apart for me not to be able to really do it. That gap obviously closed as we got older. I think three years is better than four, or even five would have been a bit better because it would have been obvious that I couldn't have done the things she did. We became the best of friends though and even had a very close relationship growing up. She really looked out for me. I think it would have been easier if we had been put in different activities when we were little so I wasn't always trying to be as good as she was. FWIW.

My kids are 4.5 years apart, now almost 3yo and 7.5yo. The great things about this age gap totally outweigh the tough stuff. No jealousy issues, the oldest one loves to help with the younger, and honestly they do play together oddly well, maybe because they're both the same gender. Some of the downsides have already been mentioned - there are things we can't/won't do as a family (overseas travel or even Disney) because it's too hard with a toddler in tow (naps/meltdowns.) The babyproofing problem wasn't as bad for us; the little one had access to a million matchbox cars and stuff like that which is really meant for 2+, but we just had to be very vigilant.

The biggest problem, which I may post as a spinoff question because it is killing me right now, is that the little one apes EVERYTHING his older brother does / says / plays with. It's adorable sometimes, but excruciating at other times. My oldest is in that phase where he thinks it's hysterical to say the word "butt" or "bootie" every 10 seconds - words he never really heard until K. Now I have a toddler who delights in announcing that he's "going to shake his bootie" which gets you some interesting looks at church. Also the younger one desperately wants to play with everyone of his brother's toys and friends - we now try to take him out of the house whenever the older one has a playdate to keep him from clinging, and the lego thing has become a nightmare (his brother is in a big Ninjago phase so the little one is constantly grabbing his creations, screaming because he breaks them and can't put them back together.)

Anonymous wrote:My kids are 4 and 7 months. The only downside that occurs to me is that my 4-year-old is very into toys with lots of tiny pieces, so there is some additional childproofing to figure out. Otherwise, so far I highly recommend.

OMG, yes, I forgot about this! (I'm one of the PPs). My daughter finally got to play with Polly Pockets (I curse thee, teeny tiny clothes and pop-off heads) as well as scissors, crayons, coins, and the like... and now I have to hide them all away. Because my 4yo DD -- although she's safe to use them herself -- is totally unreliable when it comes to making sure they're put out of baby's reach. And let me tell you, baby likes nothing more than to put every little teeny thing in her mouth. Argh.

My kids are 4 and 7 months. The only downside that occurs to me is that my 4-year-old is very into toys with lots of tiny pieces, so there is some additional childproofing to figure out. Otherwise, so far I highly recommend.