Hiking in Yosemite National Park is an amazing way to get exercise while enjoying nature without even realizing how much exercise you are getting. Unfortunately Yosemite is a couple hours (round trip) drive from Fresno so it can be tough to get all your exercise in during a single day. Another challenge is that the last part of the drive to Yosemite from Fresno is very twisty roads so you may want to avoid any night time driving.
There are some great and relatively inexpensive motels and inns just outside of the park around Oakhurst. The advantage of these is that the prices are typically less per night that the hotels and motels inside Yosemite. The disadvantage is that you waste time driving outside the park, may miss out on some of the night time events inside the park, and may spend more for multiple park entrance/exits.
In lieu of adding these extra complications to your trip consider staying inside the park. If budget is not a consideration there is The Ahwahnee which offers an amazing world class elegant environmental with a gourmet dining area and to die for scenery. Less expensive is the Wawona which is still quite expensive. It is designed almost like a plantation mansion with whitewashed walls. If you stay here make sure to bring your cell phone as many if not all the rooms have no telephones. Additionally this may not be advisable for traveling with children because many if not all the rooms have no televisions. A bit less expensive is Yosemite Lodge which would remind you of a Best Western set in the forest.
The best option for the budget traveler is the campsites. If you already have camp gear pick one of the basic camp sites which are usually less than $50 a night depending on the night. If you do not have camping gear, or don't want to bring it there is the Housekeeping Camp, Tuolumne Meadows Lodge, and White Wolf Lodge which offer canvas tent cabins and hard sided cabins for about $60-$80 a night depending on amenities. These are near hiking trails and some sites include campfire ring. Additionally you can purchase packages that include the camp, bed rolls or beds or cots, and everything you need to make Smores for about $90 for a family of four.
If you want an extreme hiking opportunity you can do the High Sierra Camp. The camp is located in the back county and allow you to hike deep into the forest without the weight of tents and cooking gear. Accommodations include your lodging, and breakfast and dinner. They are typically offered on a lottery basis due to high demand but you can always check the website for last minute availability. If you are a bit flexible on while of the many high sierra camp sites you stay at you can usually find last minute camp sites for almost any day. The camp site that I found most available for last minute and booking is the Merced Lake one. This camp is a 14 mile hike from the nearest parking area, near hiking trails, near lakes for fishing, and includes dormitory style lodging with both breakfast and dinner provided in a dormitory style cafeteria tent. The price of this site from experience is around $110 a night. If you are flexible with dates you can often find last minute availability at Glen Aulin, May Lake, Sunrise, and Vogelsang sites.
Decide if where you want to stay, either the Yosemite Village, Curry Village, High County, or other area. Each of these are convenient to a different set of hiking trails, although there is a bus to take your around to different trail heads.
Decide the type of accomodations
Next decide what type of accommodations you want. Do you need to have a telephone and television provide? If so avoid the Wawona. Do you need a full hotel room then you may need to go for Yosemite Lodge or Wawona or Ahwahnee. Are you ok with a tent cabin if it saves money? If so consider some of those sites. If you are ok with tent cabins but want fire ring then think about the Housekeeping site. If you want the lowest cost option think about bringing your own tent and using a general camp site.
Consider what extras you want. You can purchase meals such as breakfast, box/sack lunches, and dinner. In general only the High Sierra Camps include meals with lodging if you don't also book and purchase a meal package. Even with the High Sierra Camps box/sack lunches are typically an additional fee. The High Sierra Camps typically only include breakfast and dinner.
Think about what events such as fire safety training you want to participate in. There are guided hikes, camp fire lessons, horseback riding tours and more. In order to make the most of your time here plan ahead so you can sign up in advance for these, as applicable. Additionally many of these have a fee associated with them so the cost of these could affect your budget for lodging.
Consider Add Ons
Think about the add on you may want. Many of the lodging options have a menu of add on options you can choose to include for an extra fee. One of the more popular add on options for those with children is the Smores option. In select tent cabin areas you can pay a bit extra and they will have everything you need for a family of four to make Smores. Another common add on is bed rolls if you choose a tent option but don't have sleeping bags or want to pay for the tent cabins with cots or beds.
What to Bring
Many of the stores in Yosemite offer anything you would ever want for safe. However the prices are often well above what you would pay at a discount store such as Walmart. Therefore to really save bring your own sunscreen, bug spray, water, snacks, and if you are not staying at the High Sierra Camp also meals. A great budget option for meals is to bring supplies for sandwiches.
First Aid Considerations
Additionally to save on OMG I got hurt and need to buy X costs bring your own first aid kit. This, based on my experience should include antiseptic, aloe vera for sun burns, band aids, rolled bandages (in case of sprains) and a fabric knee brace (in case of sprains). You also might consider treatments for bug bites.