take mom to the park
May is generally a beautiful time of year no matter where you live, so make a picnic lunch for the two of you and hit the local park. Enjoy a leisurely lunch, take a walk and have a nice chat. Odds are, she'd rather do this than be cooped up in a busy restaurant.
a gift from the past
Scrapbooking is all the rage, so why not track down some old photos that represent the different eras from her life. If you can find them, include photos from when she was a child until the present. This may be a little time consuming on your part and require a bit of creativity, but giving your mother a retrospective of her life will be a gift she will never forget, and she can even add to it with photos from future events and family gatherings.
If scrapbooking isn't your thing, find other fun ways to display photos from your mother's past and present.
take a class
If your mom already enjoys scrapbooking, why not take a class with her to create something together. If scrapping isn't high on either of your lists, then how about a card making, painting or exercise class? Whatever you and your mom enjoy, the bottom line is she'll appreciate the time you spend together and you just might share a few laughs in the process.
relax and enjoy
Pamper your mother a bit and take her to the spa. Enjoying a mani/pedi together is a wonderful way to show her you appreciate her while reaping the benefits yourself!
brave the crowds
If you do decide to go out for lunch, make a day of it. Hit your mom's favorite restaurant and then check out a few flea markets, garage sales or antique shops. Afterwards, grab coffee at the local shop and bond over half-caff double lattes.
the end result
It's really all about spending some quality time with the woman who raised you. You don't have to get fancy or spend a lot of money, just make her feel special and take her somewhere she'd enjoy. Whether going to a museum or participating in a 5K run, the memories of the day will last far longer than a bouquet of roses ever will.