The lens will be more important than the camera body.
The popular wildlife lenses seem to be the Sigma and Tamron 150-600mm zoom lenses (both companies make 150-600mm zooms). Most photographer want to be able to get to 600mm (when needed) for this type of work, but it can be difficult to find your subject if you just had a 600mm lens. The ability to zoom out, find your subject, then zoom in... makes it easier to use.
Canon doesn't directly have a lens in this range. They have the EF 100-400mm f/4.5-5.6L IS USM II -- which is an excellent lens (optically the best) but then you'd need to couple that with the Canon Extender 1.4x III. But the extender shifts the focal ratio f/6.3-8 range and to have working AF at f/8 requires a recent mid-range or high-end body such as an 80D or above. For this reason, I probably would go with the Sigma or Tamron. Several regulars here have these lenses and have uploaded sample shots.
You'll notice some big price differences ... partly because both companies have maded 160-600mm lenses for years and have somewhat recently refreshed with newer versions. The newer versions are more expensive but have improvements in areas of focus, image stabilization, etc.
At this point you can pick your camera body. The least expensive body with the best focusing system is the EOS Rebel T7i... it has a 45 point AF system where all AF points are the better "cross type" AF points. (only a good option if you use one of the Sigma or Tamron lenses).
There are certainly less expensive camera bodies. The best of the lower-priced cameras is the EOS Rebel SL2. This camera has the same image sensor as the T7i... and most of the T7i's features. But it does NOT have the 45-point all cross-type AF system. Instead it has a much simpler 9 point AF system and ONLY the center point is cross-type. The SL2 has a small compact camera body (considering it's a DSLR and most DSLRs are large and bulky). Some people love the small size. Some people find it's a bit too cramped to be comfortable.
Now about Saturn and Jupiter....
Jupiter will reach "Opposition" on May 8. "Opposition", in astronomy, refers to the idea that as the planets revolve around the Sun with the inner planets moving faster, those inner planets (and in this case Earth) will "pass" the slower-moving outer-planets. "Opposition" is the day when Earth "passes" Jupiter. The word "Opposition" refers to the fact that on that day, Jupiter is positioned in the "opposite" direction relative the Sun.
But it's significant because this is the day when Jupiter will appear the largest (for technical reasons due to orbits not being perfect circles but slightly elliptical, sometimes the day when we are technically closest is not the same day as opposition, but it's usually pretty close).
You're possibly wondering why I'm bringing this up...
When Jupiter is nearest to Earth (and appears as large as it will be for the year), Jupiter's angular width is a mere 45 arc-seconds. Compare this to the Moon... which is typically about 30 arc-minutes. In other words Jupiter's size in the sky is about 1/40th as wide as the Moon. So that's pretty tiny.
You can see Jupiter and it's Moons even in a pair of typical bincoulars. But it will appear to be a bright dot... accompanied by 4 less-bright dots. You wont see any detail. To see detail you need magnification.
With a 600mm lens and an APS-C sensor, you're getting a magnification of about 22x.
When we use telescopes to look at Jupiter (say... an 8" SCT with a 2000mm focal length and a 10mm eyepiece) we're getting a magnification of 200x ... considerably more.
This means that you'll be able to "see" Jupiter and it's moons... but you wont resolve any detail other than tiny dots.
Here's a simulated field of view that I threw together using Starry Night Pro Plus 7 (which is what I use to plan my viewing and astro-imaging).
The above image is set to roughly 11pm Eastern Time on May 8 (not counting for DST). In this image Europa is just a tiny bit below Io ... so the software doesn't draw the label or they would be unredable.)
The orange box represents the accurate field of view for a 600mm lens on an APS-C camera.
Saturn is at Opposition on June 27. It's farther, smaller, and would be a bit more difficult. When I simulate the view, it's a struggle to see the rings. You probably wont get very clean separation without more magnification.
An easier, better, and more affordable way to see Saturn's rings... is to either find a local observatory or a local astronomy club and find out when their public observing nights are scheduled. If it's after June 27... they WILL be looking at Saturn (I guarantee it... it's a favorite object for astronomers because it's very impressive in a large telescope.)
Astronomers generally try to find moonless nights for most observing because deep-sky objects (galaxies, nebulae, etc.) are difficult to see with any light pollution and the moon is a major source of light pollution. But planets are an exception... they are close enough and bright enough that the light pollution isn't a problem. (I have observed Jupiter in the middle of the day... it's a stretch... but I have seen it.)
