You should have no problem retiring comfortably. Here are some suggestions:
1. Make sure you and wife can achieve $241,500 in both your
CPF SA when you are 55. You will then get $1900 pm and your wife will get $1900 pm from
CPF Life when you retire at 65. So in total you get $3800 pm (or $45,600 pa) as a retired couple.
2. You can sell your 3 bedroom condo and move to a studio condo. Let's say you sell your paid up condo for $1.2m and buy a studio condo for $700k. You will then have cash balance of $500k which you can invest in 5% dividend yield blue chips. This give you $25k pa.
3. Each of your two kids contribute $500 pm. So you get $1000 pm or $12k pa.
In total, you and wife will have passive income = $(45,600 + 25,000 + 12,000) = $82,600 pa or $6,883 pm. This is more than enough if you lead a simple life.
Do not smoke, do not drink, do not gamble, do not womanise, do not overspend, do not employ a maid and do not own a car.