Hi, I checked the website for Mercer and it says the following, hope it answers your question: Just like plants are important to us, we understand that pets are an important part of many residents’ lives. Visitors are allowed to walk their dogs on the arboretum trails on the west side of Aldine Westfield. However, in Mercer’s botanic gardens on the east side of Aldine Westfield, pets are only allowed for pet portraits; owners must complete a Pet Portrait Form (PDF) and submit it to Mercer two weeks prior to the portrait sitting. Please send forms through mail, or in person to: 22306 Aldine Westfield Road Humble, Texas 77338-1071 Pets must be on a 6-foot leash at all times and must be cleaned up after. Seeing-eye and hearing-assistance dogs are allowed throughout both the arboretum and botanic gardens.

There is a picnic area across the street; however, there are tables (non-designated) on the main grounds where we ate a quick bite that day. I think they prefer you to eat at the picnic site to avoid dropped food and attracting ants. The picnic site (safer to drive over), I believe does have a play place for children (at least it did before the Harvey hurricane.)

There is no public transportation but Is only a short drive. You can rent a car, Uber or a taxi. ($)

He is correct, no charge, happy trip.