There are some wise words from wise people above! I'd just like to add my welcome and good wishes.
Family on board is a prerequisite for anything like IM (it's not the 'training' time, but the 'training then being wiped out for the rest of the day afterwards' time; when I first started, I rode 7 miles to the pool, swam for 40 minutes, rode home, then had to have a nap for an hour)
Running is very hard on your joints, which take longer to develop than muscles, so it's really easy to run lots, then get injured; a huge number of new runners get shin splints/plantar fasciitis/knee problems etc. I'd start with walking, which can also double as a handy family activity! ('I'll take the baby out, dear!' )