jjoe,
Congratulations on obtaining your licence.
I agree with foxmoth - about one hour to convert to a 172. Stay away from anyone who wants you to do 6/7 hours - they just want to empty your wallet.
The 172 is a lovely aeroplane and is my preferred choice for passenger sight-seeing flights, but of course it is more expensive to fly. Since you said you want to fly your family "one at a time", I would stick to the 152 for passenger flying. It's much more fun for the passenger to be up front and you have less distractions with no one in the back.
You said you haven't flown since your test, I would recommend several flights before you start carrying passengers. Get comfortable with making your own decisions. Depending on your comfort level, you could start with a flight in the practice area, followed by some circuits or you could plan a cross-country to an airfield you have been to before.
If the weather is good, there is no reason not to fly in the winter - in Canada, we routinely fly VFR on nice days, with temperatures as low as -20° C. The pluses of winter flying are that bookings are easier, the airspace is less busy and the aircraft performs better because of the low temperatures. However, don't forget to take some warm clothes, in case you end up stranded in a field somewhere and if you are flying over any remote terrain, consider a basic survival kit - at the very least a sleeping bag and a decent first-aid kit.
If you have extra money, do try aerobatics. You might as well do that in a taildragger like a Citabria. Then you will have learnt extra skills, which even in a tricycle gear aircraft, will stand you in good stead.
I see my mate pb84 chipped in while I was typing. He's allowed to spell licence with an 's', because he flies an N reg aircraft.
