My son goes to Little Village and he loves it. I think his teacher is just lovely, and they have nice outdoor space. Others with nice outdoor space in River Valley area include Brighton montessori, Sam's Early Learning Centre on Jalan Mutiara (off River Valley Road, near Great World City) just the other end of Jervois Rd - The Childrens Place, big outdoor space too.
White lodge just recently opened up there. Little village and Brighton montessori are always fail-safe bets in that areas. Moppeteers at river valley is good too and probably the most affordable of the lot.
moppeteers and little village seemed nice when i checked it out