Park entry permit is going to cost you $20 and it is good for seven days ... the best $20 you will ever spend. Go in the Beaver Meadow entrance to RMNP and make your way up Trail Ridge Road. Great pull outs along the way, road climbs to 12,000 feet, and wildlife sightings along the way should be abundant. As mentioned by others, take snacks/picnic stuff with you (there is a Safeway in EP). Alpine Visitors Center, basically at the top of Trail Ridge Road, has a cafe, also. That is a good turning around point, IMO, unless you want to keep going to Grand Lake and find some place to eat over there. You will have to return to EP via Trail Ridge Road ... and on weekend days for sure, traffic can be very heavy. But it is all worth it for the views, the short hikes off the road with your little one, and the majesty that is Rocky Mountain. Enjoy.