Music/Park Party 1yr

My son is turning one at the end of April.  Not warm enough to swim, but too nice to be inside.  After looking over this site for ideas I noticed that all of the First Birthday ideas had a tendency to center around the guests that were coming, and not the birthday child.  All of the ideas were great and very inventive, but I wanted to do something that was more just for my son(even if he is only 1).  However I do understand that you don't want siblings/kids running around causing mayhem. With this in mind the park seemed the most obvious answer. The party will be held on a Saturday from 10am-12pm.  Our park has a great fenced off section for small children as well as a big area for older kids.  There is a paved pathway that circles around the park for bikes etc, and a pavilion with picnic tables.  The theme of the party is actually music b/c my son LOVES music.  INVITATIONS: I have chosen to create and email the parents b/c they are from 2 different classes. ACTIVITIES: I am going to do a lot of the activities he does in his Little Gym classes.  The parents and children will be doing parachute activities with singing; bouncing balls on parachute,laying the kids down underneath while we lift and sing, sitting them in center while we walk in a circle and sing etc.  The children attending are in his class so they are comfortable participating. On the invitation I am going to suggest that the parents bring a riding/walking toy and/or bikes,skateboards,skates for the older kids to utilize the pathway.  I am going to make shakers for the kids by putting inexpensive pony beads in small plastic water bottles(used H2O are perfect) along with other instruments that we have such as drums, tambourine and rattles to use while we sing songs.  The rest of the time is FREE play on the equipment,balls and bubbles. FOOD: I am just going to serve snacks b/c the time of the party is in between meals. To stick with the theme I may do snacks that reflect the songs we sing.  For instance mini muffins for The Muffin Man song; ABC Shortbread cookies for the ABC song; mini bananas for Five Little Monkeys(you get the point).  I am making a small cake in the shape of a drum for my son, but will make cupcakes for the guests which will also be decorated as drums.  I thought this would be easier for the kids to eat and a great serving size.  DECORATIONS: I am going to stick with tons of Helium balloons in a rainbow of colors that will match the tableware which has instruments on it.  GOODY BAGS: Even though they are young the goody bag is a must for a birthday party. I am going to put a box of animal crackers, pinwheel toy, their shakers and a med size bouncy ball in the bags. They can all take a balloon as well.   This should be a fairly inexpensive and fun party that all ages can enjoy :)