If the panel is "outdated", do you mean showing signs of failure as in burned buses and loose breakers? If so and it NEEDS replacing, then I'd go with a 200A service right away. If it's just old but working fine with no inherent problems, then for what you describe 100A is fine for now. If cost isn't an issue as you say, then definitely go 200A when it's time. It will only help your future resale or possible future additions (heated/cooled garage, workshop, heat pump, boiler replacement with electric heat, etc)

The 100 amp panel amy be ok now, but there are three heavy loads on it now and there is a good possibility that all three may operate at the same time: Electric stove, Dryer, and Air Conditioner. If the house has more than four rooms, I'd consider moving up to 200 amps, because if your son occupies the house, he may soon want to expand into other activities. With 100 amp service, you are limited to about 5 circuits total. A typical mix is 3 of 15 amp circuits and 2 of 20 amp circuits for a total of 85 amps. There can be only one more 15 amp circuit. Normally, there are two 20amp circuits in the kitchen.

"With 100 amp service, you are limited to about 5 circuits total. A typical mix is 3 of 15 amp circuits and 2 of 20 amp circuits for a total of 85 amps. There can be only one more 15 amp circuit. Normally, there are two 20amp circuits in the kitchen."

This is sooooo wrong!

a) There is ABSOLUTELY no "about 5 circuit" limit for a 100A service.

b) The sum of the breakers themselves is a TOTALLY useless and meaningless number.

Jem, where did you get this complete misinformation?????

Baymee, listen to Bigbird. I'd give the same advice.
A 200A service is the standard today, even for smaller homes.

Thanks for confirming what I thought I should do....install the 200 amp panel and get it over with.

the thing about upping the service is you run into other issues. i KNOW that inspectors in my area will try to, and usually will, force you to bring other items up to current code. a good friend had a bad panel replaced, the EC pulled a permit for it, and the inspector made them go back and GFCI the outdoor/bath outlets before he would sign off. heck nothing was touched on those other than disconnecting fromthe old panel and pluggin most of the same breakers back in the new one. but he insisted tha tbecause the circuit was "touched" it had to come up to current code.

With 100 amp service, you are limited to about 5 circuits total.

common misconception, totally wrong, but common. at my house i have all my 240v breakers in the outside panel. there are 2 100A breakers, 2 60 amp breakers, 4 50A breakers, 2 30A breakers. that is a total of 580A! do i have 600A service, NO. i DO have 300A service though( i posted before that it was 400, but a friend who is a sparky corrected me). 1 of the 100A breakers feeds my indoor panel which feeds all the 120v circuits inteh house. this is a 24 slot panel with 22 20A breakers in it(the whole house is wired with 12/2 even the lights). that is 440A worth of breakers!
you can have 20000A worth of breakers on a 100A service. it is not the size of the breaker, it is the size of the actual LOAD that determines service size.