Unless there's something I don't know about, you don't need reservations. Just walk up and play. We haven't encountered waits, but we generally don't go to WDW during the busiest times.
I would recommend Winter Summerland for families with smaller children. It's a very, very easy course that is very cutely themed. We enjoyed Fantasia Gardens more. It also had very enjoyable theming, but it was more challenging course appropriate for older kids and adults.